I bought the RK II last year thinking at the time that it would be the last amp I'd ever need... needless to say, it wasn't.
I've gotten some good sounds out of it, but overall certain things just started to really annoy me with it - here's a rundown:
1. The clean channels
Everyone talks about how the RKII has some of Mesa's best cleans ever cause they're out of the Lonestar etc... I completely disagree, in fact I like the clean on a plain Dual Rectifier better than the ones on the RK/Roadster. I've never found a clean sound I liked on the thing and I sat there literally for a whole day trying the 6 different modes on the 2 channels, different power tube combos, etc. It has way too much "spank" if you will, this sort of honk when you pick, I really dislike that kind of sound and nothing I tried would get rid of it. I put compressors in front of it, tried adding gain/breakup etc.
My PodXT honestly sounds better for cleans.
2. The lead sound
I had a very hard time getting a smooth yet cutting lead sound - Channel 3 Vintage is what I use for it and there's just not enough of that liquid singing type lead that I want to hear. I thought about trying a boost pedal like the Maxon everyone uses with Rectifiers but I'd already decided to get another amp at that point.
3. The low end "sag"
I know this is my own fault for getting a Rectifier, cause it's part of that sound, but we started writing a few songs that needed some tighter sounding lower stuff and it is just flat out impossible to get this amp to not have that flabbiness in the low end. It's almost like the note/chord keeps resonating after you mute it.
4. Switching
I was pretty much almost immediately sick of the pedal tap dance and decided I needed to get a MIDI system going to make it so I only have to press one button to change channels and effects. Little did I know when I initially bought the amp what a pain it is to do that. I would have had to buy not only the MIDI pedalboard but some really expensive custom switching gear from someone like Axess or RJM to be able to control all the functions on the head. Mesa only gives you 1/4" relay jacks for the channels, solo boost, loops, etc...
Anyway... the VH4 pretty much blew it away. Uwe Salwender was nice enough to let us stop by his shop in LA when we were out there playing some shows and I was able set the RK right next to the VH4 through the same cab and switch between them. The VH4 has way more definition in the tone, you can hear the individual notes in a chord even with heavy distortion much more clearly than with the RK. It can get that same wall of power chords type rhythm sound as the Mesa but it doesn't get all loose in the bottom, which I loved. There was absolutely no contest between the VH4's clean channel and the RK's - it blew it out of the water. The lead channel was also much closer to what I wanted, tons of sustain even with the gain only half way up.
I pretty much decided right there to get one
If you know anyone who wants to buy a RKII next month let me know!
Ryan