The 680 has a smaller cockpit then the 40 series (no lateral knee room, some slopped panel to slice my knee caps off, manual foot pedals, no floor heater, seats worse then a Lear, didn't know that was possible), is 20 years behind in technology (C340 cabin alt controller and C421 panel layout, FADEC engines but no auto rollback on rapid D?), handles like a f!@#$ dump truck on a good day (apologies to Mack truck), has an autopilot that will try to kill you in an overspeed situation, can't fly on V bars, can't display a map on the PFD, APU's that won't stay lit, a cluster fudge of an FMS, fuel tanks that won't fill matched, can't transfer fuel, low wing loading providing a HORRIBLE and MISERABLE ride for the pax and me, and more I could probably remember if I hadn't been out of it for 10 months.
The 680 does short runways (so does the CL30) and climbs great to FL180. After that it dies, won't climb, and won't run over .68 until you're under 6K lbs gas.
Don't get me wrong, I'm fully aware of the short comings in both the LR31 and 40/45 but I'd take a 40 series any day of the week and twice on Sundays over the 680. Hell, I'd be grinning out my ass to leave it forever and get back into a King Air. Nothing about the 680 instills confidence or displays a well thought out airplane.
Again, there were eight of us in initial. The only ones impressed were those coming out of other Citations (mostly X's). The rest of us were scratching our heads wondering Whiskey Tango Fox.
JMHO. YMMV.