Hi - I've been going through the tactics trainer and I find the puzzles either too easy or plain obvious.  My actual rating is around 1900 so it's probably because I have to work myself up from the designated 1200 rating given to me on registering by chess.com.  My question is: does the difficulty of the puzzles grow as one increases one's rating from giving correct answers?  Thanks

Yes. Tactics Trainer generally gives you puzzles around your current rating. Therefore, as your rating increases, the puzzles get harder. (This explains the ~50% pass-rate people get confused about; it's because the puzzle is rated around where 50% of players at that rating will get it correct. It's the whole point.)

ah ok - great!

I play too quickly on them and make silly mistakes. :(

Another question - is there a way in which one can re-do the failed puzzles and have them count for the rating? Preferably I would like to set aside one session a week to re-do the failed puzzles for that week

Wow, it's been a long time since I answered your last question. Regrettably, there is no way to replay failed puzzles in a rated way; you can only go through them in 'practice' mode.

I may be mistaken, but I'm pretty sure the puzzles are re-rated after each attempt based on the result as well.

That is perfectly correct, TheGrobe.

Sorry if I didn't infer that strongly enough back in October, with my bracketed statement. (Post #2)

Another question - is there a way in which one can re-do the failed puzzles and have them count for the rating?

Actually, yes.  Play long enough, and you sometimes encounter puzzles you've done and perhaps failed at before.  I've seen several puzzles 4, 5 times, many of which I whiffed on the first 2 or 3 tries.

It helps to yo-yo in the ratings.  lol 

 yo-yo is the right word. I was up to 2385 and now I'm down to 2150. I'm annoyed (at myself) because most of the failed puzzles I got right the second time (in practice mode and without looking at the solution).