These things can sometimes go through the "persistent" file which is the one that holds all the variable cache. I always delete it in each new version but sometimes it can cause strange behaviors.
Anyway, I've been testing, and thanks to an option in the code I've managed to fix the current problem in 0.6 with the map (random lag/spikes) and it seems that everything is running a little more smoothly.
The solution has been to increase the image cache and now it uses a total of 500MB of RAM approximately. I have to keep testing because these things can go very well but if you touch more than you should... it explodes.
I'm glad this version is going well for you, enjoy the bunnies.