I have corsair valueselect 1gb 2x512 ddr400. Are the timings good 2.5-3-3-8?

Answer 1

Yes, that's good.

There are different lines of computer memory, for different types of users. Corsair's ValueSelect memory is for the typical user that isn't going to tweak his system much (if at all), but doesn't want to deal with memory related issues. Corsair's XMS memory is for users that demand performance, even under extreme system stress.

Answer 2

Well the lowest you are going to get on DDR is 2, so 2.5 is good. For DDR ram the timings have become pretty much uniform at either 2 or 2.5, its only on DDR2 that timings vary a lot.