I have 2 QR's, one from 2006 and one from 2013 with B+ option. LOVE BOTH.
There has got to be a bunch of threads on this, so quickly...
Cons:
3 preamp tubes means less than optimal effects loop (tone suck), although it does have one I find it unusable
Earlier models have a more "fendery" clean tone (not necessarily a con to some) but not super clean either. I find you can get pretty clean rolling the volume off the guitar.
Pros:
Huge value for what they are...
AWESOME AMPS with weird mids, LOL!!
Great "Marshally" tones, gear 1 with gain at around 1 O'Clock = VH tones
3 gears, each with a bit more gain.
Solo boost is foot switchable, as is OD1/OD2
Scott is a great guy with great staff and they will help you out if you need them.
Later models included an upgraded clean channel, 4th preamp tube and adjustable volume on the effects loop.
Also, there is now a B+ option for a bit of a different flavor, decreased voltage.
If you are looking for that hot-rodded Marshall sound, the QR delivers.
Friedman also delivers, yet a BE 100 is $3600 new and a QR is $1400 used.
I want a BE 100, but...I will have to wait for $$
Try out a QR and then you decide.