I'm at about 1.7X, moving from a Bonanza S35 with IO-550 to a D55 Baron with IO-550s. I set aside 20 grand for "hour 1" and the rest is fuel. I haven't exceeded that budget yet, which has left room for upgrades.
Some subtleties lie in the already mentioned fixed costs are comparable, hangar and airframe maintenance don't double. I usually ran my Bonanza at 75% power, whereas I tend to run the Baron closer to 60-65% (so 14gph vs 24gph) -- when it's that much fuel, running 28gph for an extra 10kts doesn't feel worth it... unless I'm showing off or feeling small and want to see 200kt on the dial
My insurance in the baron is 40% higher for comparable hull, but I have a lot more single time than twin, so that may level out over time.
The twin has a 60% higher useful load, or a nearly double 4-hours-of-fuel payload. It's quieter. It doesn't freak out non-pilots (which is erroneous of course, they don't know my training rigor or even the exotic ways the twin may try to kill them), the heater is better, the cargo space is better, it sails through turbulence that would have me crying in the V-tail. It's comforting seeing the redline on the ASI up at 258mph, I know she's gonna take a punch if I need her to.
I definitely don't take it out as often for random hole-boring, but I do plenty of "yo let's go flying" $300 hamburger trips. Honestly I think the hassle of fishing it out of the hangar from an airport 20 minutes from home is the biggest limiter, not the fuel bill.
They're fun, but I like having a plane that is somewhat "serious business" and needs me to stay sharp to fly well. I spend a fair bit of time contemplating selling it though, particularly in this strange market -- twins are gonna be the very first to nosedive when values correct.