Restarting a character, with all of his attributes, weapons and perks, at the beginning of the game is sometimes called "new game plus." Mass Effect had it, but Mass Effect 2 won't.
Preston Watamaniuk, the lead designer for Mass Effect, addressed the question today on Bioware's forums, and the explanation has as much to do with Mass Effect 3 as it does with Mass Effect 2.
The short answer is no.
The reason is progression. We have been working very hard to make sure we design the abilities system to offer smooth progression into ME3 from ME2. Allowing double progression on characters makes that almost impossible. We have to have reasonable knowledge about where a character could end up finishing all content on a playthrough. We also want to offer choice of character build within specific classes.
We replaced that feature with playing after you were done because it preserves progression and allows for smoother downloading of PRC.
I'd say "smooth progression into ME3," means that whatever happens to your character in this game, you'll have the option of inheriting him or her in the next. Otherwise, being able to play after completion will have to suffice if you're looking for replay in Mass Effect 2.
New Game+? [Mass Effect Forums, thanks Joshua T.]