I used to have an at-100 combo and besides having to add a fan to it (They run crazy hot)
I never had any problems with mine. Very Recto-ish sounding amp, loved my Recto 2X12 hated my marshall AX.
You can probably get it even cheaper, when I bought mine a buddy bought a head. I traded mine in towards a JSX, he basically gave his away
on Craigs List
Talk him down.

I'm pretty sure I've seen them go lower than that. Lower prices on ebay right now too...

+1

I saw one at GC with a blown output tranny.

Yea, the guy told me that for $400 he would sell me the head, the footswitch and a Digitech GNX3. Not really interested in the GNX3 but its worth approx. $100 used on Ebay. I was thinking it would be cool to have a recto sounding head without spending recto pricing. From the clips that I have heard this amp really does sound like a rectifier. Kind of on the fence.

I had one but the combo. Was cool but it was pretty noisy.

I bought one new when they first came out. Mine had the typical problems of the early ones. Reverb never worked, even after they sent a new reverb tank and opto couplers and instructions for the fix. The pilot light had to be replaced, and the impedance selector switch fell apart. Besides that, mine sounded fantastic, never ran particularly hot, and was reliable enough that I gigged with it for two years. We're not talking heavy gigging by any means (maybe 20 shows total), but it never let me down. I had Glen Morris do the suggested repair for the reverb, and his opinion was that it was a very well designed amp, and that the construction was pretty decent. I have a hard time when people compare them to Rectos, because IMO they don't sound very Recto-like at all. I'd say they sit somewhere between Marshall and Mesa sounds, and even lean more towards Marshall. Lots of gain on tap. Quite a versatile amp.

My friend got in quite a few dead B52's in his repair shop. The vast majority of those ended up being door stops, not worth repairing. When we run sound for bands using them their tone seemed like an annoying buzz. I'm not sure if that tone is inherent to the B52 or just guitarists dialing it in that way. As unreliable as they seemed I never got the urge to find out for myself.

I imagine that was most likely user error. I've had a ton of amps over the years, and the AT-100 is not one I would describe as buzzy. However, I guess using too much gain can make any amp buzzy. Chances are, due to the low cost, you're more than likely getting a lot of younger or less experienced musicians using them, and probably using too much gain.

Here's a couple of clips I made of mine.

http://soundclick.com/share.cfm?id=6777024

http://soundclick.com/share.cfm?id=6774263