MHO a F33 and even a 33-35 is a spectacular airplane to own and operate. I've had a Debonair (33-35) a F33 and A36. In 14,000+ hours of flying; the Boeing 757 and the F33 tie for both being just terrific airplanes that do everything they need to do with plenty of margin for safety. The "control harmony" of the 33 is just perfect, they land easy, stop well; machines that make the average pilot look like a deity. The F33 handles like a Miata, but has the stability required for instrument flying. The "surprises" are usually good surprises, like how that FAT, high angle of incidence wing and relatively large tires make easy work out of short and soft fields. We tend to think of an F33 as a serious cross country machine, and it is, but it does fly-in sort of missions well too. Just a great all around aircraft.
There is absolutely nothing wrong with the 0520, but the O-470 (33-35) and the later model O-550's are the more bulletproof, longer lasting, motors. If you decide to operate the engine "lean of peak" ensure you have good engine monitoring equipment and take the time to learn the technique. I've operated mine for years reliably - tried to teach it to my partner in the A36 and he managed to burn all 6 exhaust valves between annuals.
There are many mechanics familiar with the type and they are easy to work on. That big open cowling really is a safety feature. Take a look at the logs for fuel bladder replacements. Look for corrosion in early airplanes. Be aware that the old King Flight Directors and old autopilots can be expensive and time consuming to keep running in their final days. They are not a "deal killer" but ensure they are completely squawk free before taking the airplane.
If you are somewhat inclined, the Boananza takes kindly to owner-maintenance. Get the right lubes and keep an eye on bearings - save yourself money over the long haul. If you keep an eye on your own airplane at 50 and 100 hours, or know a mechanic who can kind of walk you through the finer points of "progressive maintenance" then the annual inspections are no big deal. If you show up for an annual with a squawk list coming in the door; it can get expensive. Join the American Bonanza Society. They are a treasure trove for operational, maintenance and just all around good ideas.
Bottom line, the F33A is a very confidence inspiring airplane. Looks great and flies even better.
The A36 (for only being about a foot longer) is a whole lot more of a truck than the F33. It is heavier on the controls and while it is capable, I've never found the A36 to be as much fun and I'd be less inclined to do some of the flying I have done with an F33 in the 36. Just got out of a King Air 200 yesterday and just like the A36, it is very capable but not something I'd do an extra touch and go in for fun.