People been hatin'on Peaveys for years...I just don't get that...
I won't say "hate" in my case. And Sneaky got great sounds out of his Session 500's - but he was using a heavily modded Fender 400 with tons of effects, plus the amps had been tweaked by Red Rhodes.
IMO the solid-state amps just don't have the warm tone I prefer, which generally requires a good tube amp.
From a teach standpoint, I have worked on both solid-state and tube Peaveys. And while I will give them credit for supporting the step community and selling amps that are relatively inexpensive, the build quality is, IMO, weak. Tube socket mounting on circuit boards, solid-state boards that are lightweight and connected by ribbon cables and snap connectors (rather than eyelet or tagboard wiring are simply not as robust as, for example, Fender's blackface & silverface tube amps (the reissues I dislike for the same reasons I gave for Peaveys).
First I want to hear good tone that's capable of easily being voiced to a player's liking - with Peaveys that's a difficult thing to do.
Second I look for build quality - solid wood cabinets, hand-soldered wiring, no surface-mount components and ease of service. That description does not fit any Peavey amp I have ever seen or worked on.
But used ones are so inexpensive I petty much consider them disposable amps. If something major is wrong it may be more cost effective to replace one than fix it.
But to return to my first point - for the majority of uses, the range of tones available from any Peavey amp does not suit my purposes. Too much headroom, too little warmth and overly stopped mids.
One caveat - it seems like many of those who dislike Peavey amplifiers come, like me, from the 6-string world, and cut our teeth on Fender, Vox and Marshall tube amps. And Peaveys just don't seem to hold up tone wise to any of those examples. Again - MY opinion. I'm not saying they are bad amps - I DO feel there are many that are better built.