I've yet to score a bigger drive RMA'ing an old drive. On Harddrives or CDRoms. Even after friends scored better models. And I wasn't cheating, all RMA's I've done are for actual bad drives.
Even at 2.99 years, (lucked out a few times) they had stock of the old drive and sent me it as a replacement. I believe that was an 8GB, it's been a while since I've had to do an RMA. I think I'm about to do one on my Maxtor 80GB I just bought from Staples... it makes a clunking noise at random times (no drive activity). It's possible it's my other drive, 20GB that's doing it. I haven't done any swapping yet... but I have everything backed up on another PC so I'm not worried.
Oh, speaking of that, did you know that they don't renew the warranty on the drive when they send you a new model? That's right, if you get a replacement drive at 2.99 years and send it back, the replacement has a .1yr warranty.
Thus, I'm disappointed in the 1yr warranty now being the standard, but can't do much about that. I'll just have to upgrade and backup my drives more often. Of course, exactly what the reason for the 1yr warranty. D'oh.