It may be fine, but it might not. Unless you're willing to buy something, spend a few days debugging it, and ultimately throw it out, it might be better to buy new. I wouldn't get the AT&T thing on eBay - "all sales final" - even though it's new. AFAIK, AT&T isn't known for 802.11 parts. The Linksys thing seems to have been a little pricey to me for "display" 802.11b parts (even though it came with the PCMCIA card).
At the moment I've got a Linksys 802.11b WAP, a D-Link 704P Ethernet router/switch/firewall/DHCP server, then about 30 feet away I've got a D-Link 802.11b wireless bridge which connects to another D-Link switch. I've got a Motorola cablemodem. (Use the Site Search to find the model numbers - I'm too lazy at the moment).
When everything works, it's great. It works with my T41 laptop and my wife's Ti Powerbook G4. But it seems like I need to unplug the cablemodem and turn off the 704P and the WAP to clear out whatever problem they have (symptoms: very slow response to web sites, slow FTP, slow connection to e-mail). After the power cycle, things generally work well for another day or so or more.
A few months ago I thought that updating the firmware solved the problems, and it did help, but something is still going on.
802.11G is faster than B (54 Mb/s vs 11 Mb/s). You likely need G (or A, or 100BaseT or faster) if you want to use MythTV over the [link|http://www.mythtv.org/docs/mythtv-HOWTO-21.html#ss21.17|network].
G is newer, can talk to B devices, and often claims to have longer range, etc. There are differences in the security options, WEP bitness, Firewall options, DHCP options, etc., etc. that can account for the price differences between various boxes. Brand has a big impact on the price too. I'll bet most of the consumer grade stuff uses chips from a handful of manufacturers with slightly different drivers (rather like graphics cards). By now G parts probably should be newer than B parts and should have more of the bugs worked out - but there are not guarantees (as we know from Peter's experience).
All of this wireless stuff seems to be a crapshoot at the moment. You can have people say the same item is perfect or crap. Apparently it can be especially bad if your neighbors are also using wireless stuff (as there are only a few available channels).
If my recently purchased G parts work out, I might have some B stuff available for a very reasonable price in the next week or two. (I don't have a PCMCIA card, but if your laptop has an Ethernet port all you need is a CAT5 cable to connect to the bridge. You really only need the card if you want full portability.) I'll keep you in mind. :-)
Bottom line: If you're not sure you need G and are just starting out, getting hand-me-down B stuff might make the most sense. Don't spend a lot on it as G parts are getting fairly cheap.
HTH.
Cheers,
Scott.