I've been simplifying my rig over the last 18 months and gave up my Digitech 2112/Mesa 20/20 rack. I lost all sorts of capability in that move. I went with a pair of Super Champ XD's - which were good but nowhere near as flexible. The Mustang brought that back - I can go from a classic Fender sound to a pretty loaded up AC30/Marshall sound with one click of the footswitch.
BTW - the 4 button FS is on backorder for me - it has a numeric display to show you what preset you're on - for now I have to look back to see where I am.
The tuner is extremely sensetive - similar to the Boss LCD tuner with a simulated needle (maybe 80-100 pixels on each side of 0) to show sharp/flat. I can move it one pixel by just touching the string near the tuning machine.
It seems like Fender has gotten dsp based tube emulation down (finally!) The PC based UI (connects via USB) allows advanced tweaking of the tube amp sim paramters (on the Fender models) including tube sag and bias - I can get the old Super Reverb squeal (when you really jump on a high note) down by cranking the bias and sag.
The 12" Celestion and open back cabinet have plenty of clean bass. 100 watts is plenty of headroom - I've got the gains in the presets in the 4-6 range and only need to run the master on 4-5 (why do all bands slowly get louder as the night goes on?)
The other guitar player in my band is going over to the same amp and we'll load my presets from my PC into his amp too.
Charlie Davis is my guy at Sweetwater - tell him you got his name from me.