Blitz, helpful or harmful?

I've heard arguments for both sides. Is blitz chess a good way to improve, or does it create bad habits?

both!  It can expose weaknesses in your game, especially openings, by showing you obvious reasons not to choose certain lines.  It can also help you develop your tactical skills by making basic tactics second nature.  

The down side is that the more blitz you play, the more your brain gets used to chess at that speed, which will naturally make you more impatient and error-prone in slower games.  

Playing rapid chess, one can lose the habit of concentrating for several hours in serious chess. That is why, if a player has big aims, he should limit his rapidplay in favour of serious chess.  -  Vladimir Kramnik

 Blitz chess kills your ideas.  -  Bobby Fischer

 I think it depends on what level you are at right now.

My OTB play improved dramatically after I started playing online blitz, but I'm still a pretty weak player. 

 Blitz is a great rapid tool for teaching you to not leave things exposed, and perhaps a little bit for learning openings, but even at my level I found myself "rushing" my thoughts in OTB games after I had been playing a lot of blitz.  If you are serious about Chess, and have at least four digits in your rating, my guess is it does more harm than good.

 I wish I could last 5 minutes with a beautiful woman!

I play it for fun only - serious games will be analysed first by myself and then by Fritz.

Serious games are tournament games, usually classic/standard time controls. I take rapid games less seriously and blitz is for fun/relaxation.....  

I think sometimes beginners don't realize chess is a skill like anything else (it's not some mystical game of pure brain power where only the smart can win).

And like any skill you build it with practice, both the good and the bad.  Repetition helps make things permanent.  Not sure how many are familiar with music, but it's very possible to practice your mistakes.  Only perfect practice makes perfect.

I really like the Fischer quote Reb gave about blitz killing your ideas.  Blitz only allows you to play what you already know very well.  And the faster you can find decent moves, the better you will be.  In long play it's the quality of moves that count, which is why blitz play (practicing quick decisions) hurts your long play (where comparatively minor mistakes get punished).

You get better by pushing the limits of what you know, and trying to incorporate the new things you've learned in a useful way.  Blitz only gives you the time to play ideas and patterns you're already very familiar with.  Where there's no practice, there's little improvement.

If you're completely unable to play blitz and you're new, it can be good practice for recognizing threats (you get to practice it at a much more efficient pace).

Sure, only the titled players can play "serious" chess if you equated it to the quality of play, but honestly :  if an adult player regularly invests 1-2 days of his weekend (or weekday!) to travel to a location + compete in back-to-back games with slow time controls against opponents who may be way stronger than he is (which is the norm in Swiss tournaments where you can't pick your opponents), I'd say there's a level of seriousness a few rungs higher up on the ladder than a guy who sits behind a computer screen playing it online. 

"Seriousness" is the level of performance you demand from yourself.  At the coffee shop in a G/15, I'm not going to demand my moves are the best that I can possibly come up with.  If I see an interesting idea, or a tricky trap, I'll likely play it for fun.

In online blitz, there's really no incentive to push myself to 100%.  There's no cash involved (even if it was just the gas to get to the tournament) and the rating isn't going to impress anyone, so it's just for fun.

At a tournament, even if I'm not playing for a title, I'm going to set certain expectations on myself about the level of play I can achieve.  If I manage to play near 100%, then my won games will be cherished memories and the losses will be invaluable lessons (although there is some cross over both ways :)

I honestly can't even remember the opening of my last blitz game, or if I was even white or black :)  But I still remember the position where I let this expert sac his rook on e6 in a french and get a winning attack (maybe a 6 month old game ;)

You ever invested a few hundred dollars and a week-end to play in an otb chess tournament ?  My guess is no given what you said above. Believe me, these games are "serious" to those playing them, amateurs or not. The reason OTB is, in general, more serious than net play is precisely because of what people have invested in the OTB games.... 

The tourney players who don't take it seriously (and you can usually tell) inevitably stop showing up.  It seems your case was no different.

No, there's nothing wrong with that :)

There are a million different activities that people take very seriously that I couldn't care less for   To each his own.

Then you simply are not a "serious" chessplayer. I am and so are many other amateurs. It gets more serious the better you do in the tournament. If you make it to the "money game" its very serious. If you dont take your games seriously then you are not likely to improve and thats fine if you don't care but the majority of people I know who play in tournaments are trying to become stronger

players. 

Whatever floats your boat... 

Sure.  Playing chess for fun doesn't mean you can't still beat the crap out of people at the game

I think I see a consensus here. I think I'm going to approach blitz as a sort of warm-up before longer, more thoughtful games.

Unserious games are where you allow yourself to potentially lose against weaker opposition