Skittish isn't a word that springs to mind when describing an IO-550 powered 210. The only difference I've ever noticed was the 2700RPM redline, a higher fuel flow for a given power setting and slightly better performance at altitude.
I never had cooling problems in the aircraft that I flew. Having seen some recent (woeful) engine re-installs after engine overhaul I would suggest the cooling problem probably had more to do with the incorrectly installed, unrefurbished engine baffling than with the engine itself.
The 'R' model 210 is the nicest I've flown. No bobweights, downsprings or aileron/rudder interconnect springs hooked into the system. It was a revelation. Never dreamt of using the word delightful and Cessna 210 in the same sentence. In some respects (I did say some, Chuckles and FTDK) perhaps even better than the much admired and imitated V35/A36.