If it makes you feel any better, I bought my 325i almost 4 yrs ago as a CPO w/23k miles on it and it has always done what you describe (definitely just a brake pad issue; not differential or brake booster). The brakes are "sticky" just as I come to that last couple of inches to stop or take off from a stop, making it difficult to be completely smooth. I mentioned it to the service guys the first time I took it in for service and was told they're working as designed. I'm still on the original front pads w/about 60k miles and just changed the rear pads and flushed the brake fluid several weeks ago; no difference in braking (changed the fluid a couple of years ago also with no noted performance difference). Great brakes so I can deal with the minor stickiness at a stop. I may consider switching to different front pads (non-OEM) when they're due as you'll find some great recommendations here, but I've been satisfied with the performance.
A longwinded response but in a nutshell - I wouldn't worry about it.
BTW, I've driven a couple of newer 3's as loaners over the years - slightly less brake stickiness than mine but very little difference. It's a design thing. Search the forum for good pad recommendations.
Last edited by dallas70; 10-27-2012 at 05:16 AM.
Reason: Extra info