i memorize to some extent. i wish i could remember more.
How far can one get without memorizing lines?

The way I learned to played (the Josh Waitzkin school) put less emphasis on memorizing opens and more time working on tactical play and strategies. The sublties of openings is lost on absolute beginners. However, you need to have a flrm grasp of opening principles or you're lost. With this in mind, I may be down a few material points in the beginning of the game but I make up for it later on. You should know repsonses to various openings but simply memorizing opening lines and concentrating all of your efforts there can lead to problems. I spend most of my time studying (4-6 hours a day) working out middle and end game tactics. I eact chess puzzles and problems for lunch. Sound tactics will win you material when it counts. I have come back from a serious loss in material to win games. Now I am by no means anywhere near being a top rated player (or even a good player), but I do alright for myself in many games. I use the Lev Alburt books as well as a number of tactical books to help my game.
now I am by no means an expert at chess, but i know that the best computers play chess by the move
if that means anythign

About 80% of my opponents have lost by inaccuracies in the opening...
So yes, you have to know the opening - not simply by rote, but alongwith understanding the principles, and the game is so complex in the openings, that without basic knowledge of the openings, it is so easy to make the wrong move.
There is no substitution for hard work.

Van Wely says he didn't start serious opening preparation until he was 2400+.
Of course, there may be various degrees of "serious". Knowing a few moves of the openings you play is useful. But losing material in the opening isn't a sign you should learn the opening better, it means you should learn to notice simple threats...

It also depends on what openings you use. Some variations have a vast amount of theory attached and you need to know some of it or else you will suffer. Other openings are very 'trappy' and you need to know what to look out for or you will get caught out. Other openings are more like 'systems' where it is not so important to do too much memorisation.
I agree with some of the points above - you can't really understand the reasons behind the move choice in the books if you don't have a grasp of strategy and tactics, but at some point it will become essential to memorise your chosen lines to a greater or lesser extent. It is possible to come back from a poor position or a material deficit in some games, but when you start playing strong players this will become much less possible.

I got to near 1900 on turn-based sites like this after about 2 years of playing through doing absolutely no study at all. Now I'm just starting to get serious about studying, but having learned a few simple opening ideas over the last few months I don't think putting any more effort into learning openings is going to be worth my time at all. I know I can get into a playable if sometimes slightly inferior middlegame most of the time as White or Black. And at my level from then on I know the better player should win regardless of whether they've memorised all 1 Billion lines of the Sicilian Poisoned Pawn..

The way I learned to played (the Josh Waitzkin school) put less emphasis on memorizing opens and more time working on tactical play and strategies. The sublties of openings is lost on absolute beginners. However, you need to have a flrm grasp of opening principles or you're lost. With this in mind, I may be down a few material points in the beginning of the game but I make up for it later on. You should know repsonses to various openings but simply memorizing opening lines and concentrating all of your efforts there can lead to problems. I spend most of my time studying (4-6 hours a day) working out middle and end game tactics. I eact chess puzzles and problems for lunch. Sound tactics will win you material when it counts. I have come back from a serious loss in material to win games. Now I am by no means anywhere near being a top rated player (or even a good player), but I do alright for myself in many games. I use the Lev Alburt books as well as a number of tactical books to help my game.
You've done amazing Hugh, but coming up to 1800 I expect it's now becoming a bit harder to come from material down?
You can get quite far by just using common sense in your openings--develop pieces, grab central squares and move the King into safety. Also going over your games both wins and losses and evaluating the positions and looking for ways to improve is essential. Easily this approach can get you to 1400-1600 if you know you tactics.

Many Grandmasters stress that you really don't need to work on memorizing chess openings until you are at least an Expert. There are so many chess fundamentals to learn before an in-depth analysis of openings would even be worth the time. If you don't understand chess before you start trying to fine tune it with opening nuances, you will be wasting your time. It's like Fischer says, Ideas, not moves, are what's important.

If I read correctly, Bobby Fisher left the game becasue this mechanical approach was taking all of the fun out of the game.
My understanding was the opposite - that Fischer's opening preparation greatly exceeded everyone else's, and so he was able to very often get the better position after the opening.

It also depends on which openings you play. If you like to follow the GMs, you'll often find yourselves playing very sharp variations in which you must find several "only moves" in a row in order to read a good position. If you want to play positions like that, it really helps to know the moves instead of trying to find them over the board.
But in openings that aren't quite as sharp, memorization plays a much smaller role.
So don't be a fashion victim, play solid stuff :-)

I don't think it should be an argument for or against memorizing but if and when it makes more sense to memorize.
I never really 'booked up' on openings but have constantly tried to follow principles of good opening play and 'ideas', 'themes' or 'systems' as stated above. Theory and practice backs them up. There will come at a time that it makes sense to memorize them just because you already 'know' what the good vs. bad moves are without spending time to analyze (this advantage in pattern recognition and focusing gives us an advantage over computers). For OTB games, you save on precious time. That's the time memorization becomes important - but only because you understand the ideas behind the moves.
I have wondered how far it is possible to progreess using only logics and tactics. I keep hearing that if one wants to be excellent, they need to read many chess books and memorize openings. Have any of you top rated players been able to win with experience, solid fundamental play, and smarts alone? If I read correctly, Bobby Fisher left the game becasue this mechanical approach was taking all of the fun out of the game. What are your thoughts?