I have about 400 hrs in the X.
It flies best at 135-140 knots on approach, especially when a bit on the heavy side. Below that it gets a bit squirly with less airflow over the wing and ailerons. Nothing too severe when slower, just more comfortable at higher speeds. Dipping the wing on touch down in a strong crosswind is more of a concern to me and most other X drivers. Ask the NetJets guys who were flying the thing when it was new.
They since have regeared most of the first airframes which required 68 degrees input for full aileron deflection, to the 34 degrees ailerons which later became standard. You only have about 18 inches wingtip ground clearance on rotation (12 degrees NU) due to the wing sweep.
Buckets will deploy without nose wheel on the ground, but as already mentioned nose needs to be firmly on the ground or you will pop a wheelie. Ask me how I know.
Buckets are pretty fast, one second to fully deployed provided you have the mod/later airframe, otherwise I think it takes three seconds. The carbon breaks can be a bit touchy from airframe to airframe but do offer excellent braking capabilities. On longer runways there is really no need to go beyond idle reverse if noise is a concern, just as full reverse only will be enough if you are into brake saving mode. The shortest strip we do (part 135) is just shy of 5000' and , but that is under DAAP with the 80% rule.
I've only seen FL470 during a test flight, but if you really need to get low fuel burn that is definitely a usable level when light. Normally start at 400 or 410 if heavy, 430 possible if light and the right atmospheric conditions. Not many folks like being up at 490/510 for obvious reasons.
No idea on the longest leg ever flown, and no desire to beat it whatever it may be. The advertised 3000 nm "sales man" numbers is not something you do every day, at least not if you want to land with legal IFR reserves. Longest leg distance wise I've done is Zurich to Abu Dhab which was with a pretty good push from the winds. I believe it was 5=20 hrs. I recently did Cyprus to Shannon (~2300 nm) doing M.85 most of the flight, also 5+20 hrs. I've talked to guys who have stayed up well beyond 6 hours, with the power back obviously.
The airplane really doesn't like flying much below M.86. We normally go max cruise (speed is obviously why you fly on a X) if fuel is not an issue and start out at .88/89 at gross weight. You normally end up doing .91 to .92 a couple of hours into the flight.
Don't have the exact numbers in front of me but 680 pounds should get you around the pattern. Again, prefer not to be the test pilot in this case either. An alternate 15 minutes away at FL60 requires 700-800 pounds for the burn on the flightplan. Our company minimum fuel on landing (IFR under FARs) is 1700 lbs. Most guys prefer to see 2000 to 2500 on landing, or more depending on where in the world you are.
All in all I like flying the X but it may not be as versatile as some of the other super midsize jets out there.
Hope that helps.