I have a 1976 114 and flown across the country and never had to go higher than 12,500. I am VFR because I never has to be someplace at a certain time. If I did need to be there I would fly commercial - which I don't do as I never have to take my shoes off when I want to fly.
I also like VFR because I like to see the country not a bunch of fog. But, that's just me.
My 114 will fly comfortably at 135 to 140Kts at around 11.5 to 11.8 gph. Commanders 112 and 114 are very comfortable airplanes and I have found very easy to fly and land. But, it does have a lot of moving parts and depending on the quality of the airplane you get your maintenance may not be to bad.
If I was in the market I would make double, double and then triple sure that every nook and cranny of the airplane is looked at before purchase. There are many stories on here about the cost of the dreaded first annual. A search on here will give you lots of information.
If you are handy at mechanics that is a big benefit and having a AP/IA that knows Commanders in my opinion is a major plus. They are not hard to work on and one of the best things about owning a Commander is this site. There are many here willing to help and know an awful lot about them.
Visit the Hangar section and you can see a ton of resources when you need something. Good Luck and welcome to the world of Commanders!