tele_jas,
I have a MK IV. I am in a cover band that does mostly Classic Rock, with alot of country mixed in. Check out our Song List at www.nolimitsband.net to get an idea of our mix. There are sound clips there, but they were not performed with the MK IV (they are about 2 years old, and I have only had my MK IV for about 8 months.
I was a Fender Blackface guy prior to the MK IV. I love that clean sound. The BF or Tweeds, either way, I did (and still do) consider Fenders to have the absolute best, fattest, roundest, most musical Clean tone out there.
That being said, I LOVE my Mark IV! It is so darn close to the BF clean sound with my Strat that I haven't removed my Super Reverb from the Closet in over 6 months. Additionally, I have the second channel dialed in with a wonderful "brink of break up" tone that sounds like a Deluxe Reverb or older low wattage Marshall just on the edge of saturation (think blues and grinding country tone!). But by far, the most flexible channel is the Lead (or channel 3). It can take me from Clapton quack, to Classic/Southern Rock crunch, to Santana and Robben Ford with minor adjusments.
I went with a Boogie because I was tire of lugging my Super Reverb AND a crowded pedal board to every gig. The setup and break down was getting old, as was the "pedal dance" to shift from tone to tone. Now the only pedal I use is my tuner.
A word of warning, however. Give yourself some time with your new Mark IV. It took me nearly a month of experimentation and tweaking to find that perfect collection of settings. There are so many options that you need time to try them all and settle on the best for you and the guitar you are playing.
To be fair, have you tried the Lone Star Classic?? I was VERY close to gettting one of those (actually, I did take it home, but decided on the MK IV in the end). The Clean on the Lone Star is almost a perfect replica of the Blackface Clean... and the OD channel is perfect for Blues and Country. If you want any "heavy" stuff, it won't quite get you there, but it is a fabulous amp as well.
There are quite a few folks out there using MK IVs... I even know a few Blues Players that use them exclusively. They are, IMO the most versatile all-tube amps on the planet.