I've bought several laptops on eBay. All of them were Thinkpads coming off of lease, and all of them have worked well. My most recent purchase was a Thinkpad T42/p to run Windows 7, which, as I mentioned in an earlier post, has been very successful.
However, a five-year old Thinkpad T40 died on me recently. I bought some parts on eBay to try and fix the problem, and it's been an eye-opening experience.
Part #1 - New motherboard. Included one week warranty. Motherboard worked, but intermittently. By the time I figured out what was actually wrong, the warranty was expired. If I was more savvy fixing Thinkpad motherboards, I would have caught the problem earlier, but I ended up getting stuck with a $130 piece of junk.
Part #2 - New display. Billed as being in "Excellent Condition." Actual condition - display worked, but had significant damage to the bottom of the display that was visible once you turned the display on. However, these displays are relatively large (not like a DIMM module, for example) and paying the postage to send it back would have cost more than the display was worth. It turns out that PayPal doesn't care about fraudulent sellers - it's always the buyer's fault. Apparently, you can send somebody a 50 pound box of bricks instead of the laptop, and the buyer will still be responsible for paying the return postage in order to make a claim. PalPal refuses to talk to you unless you have the tracking number for the returned item.
Part #3 - Laptop, bought for parts, advertised as not booting. Result: seller lied about just about everything (except the part of the laptop not booting.) The battery wasn't new, it was five years old. The DVD was bad. The hard drive and the memory were both half of the advertised sizes.
All in all, I've had a 100% failure rate on all of the parts I ordered, even though all of these sellers had positive feedback of 99% or better.
A sample size of three isn't very large, but given my 100% success rate buying complete laptops and 100% failure rate buying parts, I'd place a strong warning on buying laptops parts via online auction.