Hi, I have two experiences buying IBM refurbs. I hope my input is useful.
About 5 months ago I bought a T21 Refurbished directly from IBM. IBM sells refurbished models directly from their website (look for Certified Used Equipment). I paid $700, for a PIII with 128 RAM, 20 GB HD, 56k modem, ethernet, Windows 2000 Pro. It also came with free speakers, a laptop case and free shipping. Delivered in two days.
It might not be the best deal in the world, but I needed a laptop for $700 fast, and I knew I wanted a used IBM over a new Inspiron.
Anyway, the computer works great for the most part. I haven't had any significant problems, but there are two issues.
#1, the battery is on its last legs. It last 1 hour 50 minutes now, and the meter never gets an accurate reading. It is definately well used.
#2, they swapped out the normal HD for a slower, VERY NOISY, one. I have gotten used to it by now, but in the beginning it drove me crazy. Other than those two issues, the computer is in perfect, spotless condition.
I also bought a refurb 760xl direct from IBM back in late 1999. I paid around $500. The computer was heavy, but had a brilliant screen, and the battery held a 2.5 hr charge perfectly. I never had any problems with that one, even after dropping it a couple of times on the bus. It finally died in late 2003. The power wouldn't start up, so I tossed it.
If you are serious about getting a T series, I recommend from the IBM site. Also, if you want to save some money, you can also get them from Staples.com and use a coupon. Again, you arn't getting the best deal in the world, but you are getting 2001 high quality at a low price.