At low altitudes (5000 feet and lower), plan on 1200 pph. At FL250, fuel burn set to 600 pph results in approximately 240 kts true airspeed. If you increase the power to 400 pph (33% increase) you only achieve 20 to 30 kts (about 10-12 %) increase in true airspeed. I flew Bellingham to Anchorage in just over 5 hours at 25,000 feet using 600pph. I landed with about 1300 to 1400 pounds of fuel left.

The pressurization is Ok, but I have seen better systems. After takeoff, cabin is climbing at about 2,000 fpm and when the pressurization controller finally starts to work, it shifts to about 2,000 to 3,000 fpm down before it stabilizes.
The system requires constant monitoring and adjustment during climbs and descents. For descent, turn the pressurization controller slowly and the cabin rate of descent will not spike. If turned quickly it will spike to about 2,000 fpm for a moment. It is definitely noticeable.

The airplane has a lot of power. I have made Sea Level to FL250 in just over 11 minutes.

However, I echo the sentiment of single engine performance without the prop feathered; it will not climb until it is feathered. The Autofeather system is not on the MEL for good reason. With power at idle, props forward and in level flight, the airplane will stall in a matter of seconds. It slows down very quickly. Single Pilot with all systems functioning would be fine. Add a malfunction or two and you could have your hands full. If operating it Single Pilot I would recommend an autopilot to reduce your work load in hard IFR or for abnormal situations. It can be easy to get task saturated in the aircraft and the checklists can be cumbersome.

In my own opinion, the airplane was manufactured by a general aviation company (not made for airline use), seems piecemealed together with the parts of several different aircraft and lacks some common design features that would significantly improve reliability and functionality.
I enjoy flying the airplane when everything is working, but if operating in a wintertime environment be careful.

The wet wing is prone to cold soaking at altitude, and requires deice even when the OAT is above freezing. I believe most other king airs and the C model have bladder tanks and are not prone to this issue. I have had a 1/4 to 1/2 inch of clear ice on top of the wing where there is fuel when it was +2 degrees C and raining. It was freezing shortly after contact on that area of the main wing outboard the nacelle only. I always do a tactile check of the wing just outboard the engine nacelles for that purpose. Also, on clear days with close temperature dew point spreads, the wing will frost over that same area as well when no other aircraft except maybe an MD-80 will (a factor in quick turning the aircraft after a long flight at altitude). For the same reason, residual ice picked up inflight sticks to the leading edge of the same portion of the main wing, when the rest of the aircraft including unprotected surfaces (e.g. nose radome and vertical stabilizer) are clean.

Good luck in your decision, hope this helps.