I've been in the valve = good, SS = lame camp for years, but that is changing. The Lab series amps are incredible, and usually very affordable. Controls (like all late 70s Gibson stuff) need to be mastered in order to get the best, but these are INCREDIBLE amps.
Never heard a Lab, at least - not yet. I work with tube amps on a daily basis, but it's always fun when transistor amps of proper design comes in to the shop. And yes, prices are usually good too. Just a shame people still compare good ones to the first fender/marshall transistor efforts, or even more recent class d amps without hearing them.
As a sidenote, last week I got this Allsound Leslie (made in Germany) 'stack' in for tube change and general service. The owner, who plays in an outfit that was active in the late 70's, wanted it tip top as the band got a 70's record reissued, and they did some shows still. He was more than surprised when I told him that it was a transistor amp, but I must say - anything you plugged into this amp sounded really good..