well, it depends quite a bit on the actual setup of the league. do you keep everyone? do you keep a few people? do you have to give up anything for keeping someone?
in a league where you keep 10-15 guys it may effect your drafting strategy by up to 2-3 rounds. but if you're keeping only a few guys then you have to realize that most of your team is NOT keepers and so you draft normally, moving a few, promising guys up by a round maybe and young studs up about half a round over older studs (for example, if you had harden and rj projected equally, you would move harden up half a round due to his age).
also, some leagues you forfeit your draft pick the next year in the round that you drafted your keeper the year before. then the premium would be the diamonds in the rough that you find late rather than scooping up young guys early.
so... it kind of depends. but one thing that probably is universal is that people overvalue the idea of a keeper and undervalue the year that they're playing. quite frankly, lots of things happen over time. who knows if you'll still want to do this 2 years from now, much less in this league. so don't go crazy picking, "huge upside" guys and leaving the j.d. drew's of the world on the rubbish heap.