I think they really nailed it on this amp. I'm going to get this amp gradually. I was originally thinking about buying 1 of these 3 heads. Carvin Legacy, V3 and Mesa Dual Rec, mainly for the 3rd channels. Legacy doesn't have a 3rd channel, but it's a good amp.
The 5150III has the guts of a Peavey 5150 with the exception of a couple of more pre-tubes. The clean channel is very fenderish, but I have to admit I like this clean channel better than Peavey's version. They have a crunch channel, can get pretty creamy, and with the right settings you can get that driven plexi sound. It's very nice (to me, at least) and the last channel would be the channel with the most gain. It sounds like a 5150 (not 6505) but a little tighter, pretty damn heavey, versatile.
But the thing that caught my ears the most is how responsive the god damn thing is. A lot of high end amps sound good, but they're not as responsive as they should be. When I was using the EQ on this thing, it responded very well to all aspects. From the sound, to my playing, to my harmonics. It really shines through.
The cons of the amp really to me are that the On/Off switch and the standby switch are in the back of the head, but they're toggle switches. They feel strong. Also, there isn't a master volume, but that's all good.
I think it's definately worth the investment, but that's just one man's opinion. Sorry if I didn't introduce myself, I'm new 'round these parts.
Sorry, forgot to mention. They have some previews/demos on youtube. Just type in "5150 III " and you'll get them.
Hope that helped.