Accusim doesn't make the aircraft particularly more difficult to fly, it just means there are consequences if you treat the aircraft poorly or push it beyond it's limits. For example, you can overheat the engine if you are not careful, but again that is only likely to happen if you are careless and are flying the aircraft on the on the edges of the performance envelope. Activites like sight seeing can be very much enjoyed even with Accusim. The P-40 for example is an excellent sight seeing machine.
I have had the P-40 with Accusim since released and have not overhead the engine once. I came close once because I stupidly forgot to open the cowl flaps before takeoff...the warning light came on, I immediately opened the flaps, reduced power, lowered the nose, and then the engine cooled down. I inspected the engine after landing and there was no damage. Matter of fact with the core updates, the cooling system is even more efficient, for example in the P-40, you can maintain max climb power while in a Vx climb.