Just got back from the rehearsal space to give the CFR12s a spin.
For the record, signal chain = KPA > Matrix GT1000FX > Matrix CFR12s
First impressions (compared to an oversized Mesa 4x12 cab):
1) Despite their size, they sound wider and "bigger" than the cab, most likely due to the wider dispersion field (and there's 2 of them of course...)
2) I played together with a drummer at rehearsal volume with the GT1000FX at about 40% (levels in the KPA were set at 0dB). They pack more than enough punch.
3) I didn't do any tweaking beforehand, just plugged the new speakers in the main outs (instead of the monitor out I used before) and it did sound fine. After fiddling with mainly EQ and some of the deeper amp and cab settings it sounded great! The changes mainly involved undoing the tweaks that were required to make the Mesa cab sound good. Especially for clean sounds it was a huge improvement, the KPA came alive with the CFR12s while the Mesa cab tended to put a "curtain" over the clean sound. Case and point: the clean patches I programmed for the Mesa cab sounded dreadful over the CFR12s, while switching to a factory preset clean tone resulted in instant tonal bliss.
Summarized (based on 2 hours of messing about):
(+) for heavy rhythm work: sounds as good as the Mesa cab
(+) for lead and especially for clean patches it's a huge improvement
(+) overall sound is more transparent and easier to tweak
(+) stereo
(+) very wide dispersion field, I walked around the rehearsal room while playing and the change in sound is minimal
(+) very (VERY) compact and easy to handle (although they seem very sturdy as well). Everyone that has hauled a Mesa XL cab up a flight of stairs will acknowledge the importance of this
(-) as of yet...none (they will look minuscule on a stage?

)
As promised a few pictures, I apologize for the quality, I used my phone camera and those are notoriously crap when used indoors.