Eland, you're absolutely right- read Reichmann, ( glider pilots) or any other noted glider authors like Welch etc and they back up the direction/rotation thing. Essentially thermals are all variations of a upward flowing vortex, with "donut" like internal rotations, and varying vertical/horizontal flows through their cross- section.
I spend over 30 years gliding and hang gliding and there is definately a "sweet" direction for any thermal, and it varies all the time. And yes as everyone has noted, only the birds get it right most of the time, but you can definately feel it when wrong, by constantly getting "thrown out' of the core, or constantly recentering to maintain best climb- oh it's all good fun- we even had the Tecnam going up on low pwr a few months ago. Returning to gliding is going to be my golf- but a lot more fun- miss it terribly.