I have a 50w 5150 III and I'm really quite happy with it.
-I use it as my "bedroom amp" in my condo because I can't crank it up here and it really sounds good at low volumes.
-I'm not sure whether I'd classify the 5150 cleans as great or not, but they're definitely better than the 5150 and 5150 II (not much of a challenge I guess).
-I can't speak to reliability because I've only had it for 6 months or something
The only real complaint I have is that the blue channel is my favourite but it's impossible to change channels in the middle of a song to clean because of the stupid shared EQ with chan one volume jump. It also kind of sucks that the power/standby switches are on the back due to it being squished on the front panel. Overall I prefer the sound it gives me to my old 6505 in a smaller package. I use a 1x12 orange ppc112 but have been meaning to swap it out for the matched EVH cab because it sounds better with it to my ears.