It depends on how quickly you want your website up and running.
I am still involved in reviewing the changes made to K 1.0.10 on one last production site. I was considering upgrading from Joomla 1.5.9 to 1.5.11 but I read several comments from users here that may put that idea back a while and I may leave Joomla as it is (or upgrade to J! 1.5.10). I haven't decided yet.
Kunena 1.0.10 was supposed to correct defects in K 1.0.9 but it also introduced a significant number of new functionality; I've spent the past 3 (or 4? - I can't remember now) weeks testing things out.
As far as K 1.5.2 is concerned, I don't know anything about it. Being the cautious optimist that I am :laugh:, I'm holding off with this version until I see the results of other people's experiences. Judging from the number of reported difficulties with K 1.0.10 this could take a while.
If I were in your shoes I would do the planning and migration from J! 1.0 to J! 1.5
anyway and I would take your old
Fireboard forum, convert it to Kunena 1.0.10, make the necessary changes you'll find in the "solutions" discussion topic (there are several) - and run your production site there. I would also install K 1.5.2 (when it's available) on a J! 1.5.11 platform as a
test site.
Upgrading from K 1.0.10 to K 1.5.x - at a later stage - should be a no-brainer.