I put one in about a year ago. The alt does make a bit of noise, but not bad. At first I thought I had bad bearings in there though.
I kind of went though a major PITA with it - pulled the old crap, installed the whole deal (including relocating a bunch of stuff under the hood), fired it up - and the alternator wasn't charging the battery.
Dealt with PPW on it, they overnighted me a new alt that day (I sent back the old one later), swapped that one in, been fine since.
Welds really nice.
"Your Jeep smells like a sweaty horse." 8/24/01, "Get me out please, I'm upside down, I smell gas." 9/29/01