finally (some week ago, to be honest) i decided to buy a Fireball 100 - and subsequently did it...
now i'm much, much poorer than before, but i'm also happier...
unfortunately i had very little time to play it (i had to leave it in rehearsal room immediately and played just 2 times with the band... :( ), but my early impressions are excellent.
1) cleans are very nice. absolutely NOT the cold and sterile tone that many describe... not warm either, but surely not sterile... it sounds a bit like my solid state Fender combo (FM212R), sharp, clear and a bit percussive, but is very dynamic and bites hard on heavily strummed notes... not the Blackface tone i like best, but surely a good clean tone. separate gain knob allows to go from the cleanest solid state cleans to a real crunch.
2) lead channel is AWESOME. i'm playing with gain between 1 and 2 o'clock (70-75%) and it's more than enough... and NO, i'm not playing rock'n'roll but a blend of gothic and melodic death metal. so not exactly a mid scoop fest a la Nile, but some serious distortion is needed. ah, it's very tight, of course, but the deal is that it has got a great TONE. very peculiar, and very much different from the actual Mesa and Peavey trend. i heard many people complain about its "scooped" tone. between "bass" and "treble" there's another knob. just turn it clockwise and your mids will magically appear... :)
3) shared EQ is not an issue. both channels can enjoy a bass boost that gives more punch withoud mudding the tone. if you need a sharper clean tone a bright switch (inactive on the lead channel) can balance things, but i don't think i'll ever use it...
4) i can't judge for the old 60W version, but clean/lead volume balance is not an issue on the Fireball100. cleans seem to be louder, but there's a "lead volume" knob. turning it on 100% gives a perfect balance... just i can't understand the need for an extra knob... they could have set it on 100% by default, i can't imagine who would like a volume drop switching to high gain!
the direct consequence is that you can use the two masters to switch between rhythm and solo volume without the need for a booster... my first impression is that the "mid boost" switch (controllable via footswitch) boosts volume enough for solos. and it - of course - boosts the frequencies that makes the solo guitar jump out of the mix.
maybe the fact that the rhythm guitarist has got a very scooped tone helps, but i don't think i'll need to switch masters for solos.
5) it doesn't like too much my overdrive, but i won't use it anyway on the lead channel... there's no need at all to overdrive anything.
maybe i'm still on honeymoon, but i haven't yet found a reason to dislike the Fireball, just many to love it!