Adding .5 PPR doesn't change things enormously to be completely honest with respect to how positions compare to other positions (i.e. RB value vs. WR value vs. TE value) but, what it does do is mix things up within the positions themselves and can create larger "dropoffs" between the tiers.
RBs that both run and catch already tend to be more valuable in leagues because of the extra yardage with the extra touches, but adding in points per reception gives them an even bigger edge than normal and even brings some guys more within the realm of being fantasy relevant where they wouldn't be so much otherwise. A player like Reggie Bush may not have a ton of value in Non-PPR leagues because he doesn't get a lot of TDs and he gets moderate yardage...but if he's going to catch 70+ passes, all of a sudden he's got some more value in a PPR league because of that.
For WRs this starts to either make up the difference between guys or increase it in some situations and tends to favor possession WRs who catch a lot of passes. A guy like Wes Welker is much more valuable in a PPR league than a non-PPR because he's a lock for 100+ catches (basically he got 3.5 points per game in .5 PPR just on catches alone the past 2 seasons).
.5 PPR is a moderate increase though, so that's something to keep in mind. If you were jumping to 1 PPR it would change things rather dramatically but .5 PPR doesn't force you to really make any major adjustments. Guys should move up or down within your positional rankings depending on how well they catch passes or if they don't catch passes at all (i.e. guys like Turner, Jacobs).
I'd still focus on RBs as normal but you'll want to pay more attention to the RBs that do more than just run the ball and are used extensively in the passing game. Guys that move up with .5 PPR in my projections are players like Reggie Bush, Ronnie Brown, Steven Jackson, Matt Forte, Marion Barber, Brian Westbrook, Knowshon Moreno, and Derrick Ward. It's not going to be a huge shift but they do have much more value when you're counting receptions.