Perfect pilots don't exist
Apart from in some people's egos =D I, for one, am always suprised when flying long haul (i.e. 2hours plus for inexperienced me) by the frequencies and units controllers want to hand me over to.
I wish I could come up with a better way of working out who to receive a service from. I'm often happy to sit on "London Information" but Brize wanted to hand me over to Shobdon when tracking up towards Angelsey. I know as PIC it's up to me who I transfer over to, but you can't help but thing they know the airspace and area better than me so they are probably more informed as to who can offer the better service.
In a similar vein, I wish there was a better way for me to predict which reporting points units will ask me for. Currently I get the request and then spend the next 5mins searching the map for said reporting point. Maybe it's just experience and as you fly around the country more you'll get a better feel for controllers and reporting points, but right now it's always a suprise...