I've used both extensively. If I could only use one, it would be ct-art. Generally speaking, the quality of problems are higher in ct-art than in chess tempo, which sometimes has lower quality, way-too-easy problems, such as hanging piece problems.
The ct-art problems are also more carefully selected than chess tempo. Ct-art also has a step-by-step process that allows you to work your way through the problem in an organized way. I would recommend using both, but with an emphasis on ct-art.
ct-art gets very difficult in a hurry. You might take a look at chess tactics for beginners. I think that for your rating (and mine!), you will find that it starts off a bit easy, but will challenge you quite a bit as well.
http://products.convekta.com/198/2/
http://www.wholesalechess.com/news/chess-product-review-articles/national-master-reviews-chess-tactics-for-beginners-by-convekta
(if you are on a newer version of Windows, you might want to take a look at this before buying: http://www.wholesalechess.com/downloads/documents/Convekta_Vista7_Fix.pdf)
Actually, now that I check, there is a newer version that should work with Windows 7: http://chessok.com/shop/index.php?main_page=product_info&cPath=7_3_11&products_id=435
I think that they are useful for different things. Chesstempo trains you in analysis and thought process - looking for candidates, doing a blunder check, re-checking the analysis as an expected line unfolds. it is impossible to maintain a good chess tempo rating without doing these things. The puzzles are relatively ordinary positions requiring accurate analysis from actual games. Master chess tempo and you will be much harder to beat OTB.
CT Art does not really require you to have an effective thought process - you can solve many of them by thinking 'there has to be a combination here, so sacrificing the exchange is almost certainly the move - I'll try that and see what happens'. What it will do is help you see tactical motifs - do ten puzzles with an interference theme and you are much more likely to see this idea in your games. You will see more at a glance. But nobody can play really strong chess without mastering analysis.
They are both really useful in developing your chess. But I would say chess tempo is more like real chess - every game has complicated positions requiring accurate analysis. CT Art-style Combinations only arise from time to time, and even if you see one, you will still need to be able to analyse it carefully before playing it.
CT Art is more fun though!
I'm finding Chess Tactics for Beginners is challenging me plenty. But then, I suck...
Chess Tempo is BULLSHIT!
Yes, you can download it from here:
http://chesskingtraining.com/products/shop-downloads/ct-art-6-0-download-english/
i stay between 1200-1300 on chess.com, and am 1300 on tactics atm at chess tempo, im trying to figure out how to improve my game and was thinking about getting CT-ART from peshka, is it worth the 20 bucks or should i just stick to chess tempo? i was also thinking about membership here for videos or chessmaster11, what do you guys think?