SS is the only micro site forum on which I regularly participate.  I don't really know why I chose that specific one over IS or DT.  They all seem to be fairly active.  I think SS probably seemed the most liberal in their policies.

I find this one (MSG) the best.

This is definately the best forum,

SS is full of people:
- telling you about every mundane thing their kid did that day.
- wishing everyone a happy birthday.
- trying to convince people you are an experienced successful photographer in a vain attempt to get them to buy your book/course.
- taking an image in the critique forum and writing a twenty step process in photoshop and posting an example that is far far worse than the original was.
- too eager to ban people who expose the resident b**sh**er

iS:
- is tooo slooowww to load
- has way too many people 'woohooing' for my liking (but I am British and we don't woohoo unless it's absolutely necessary)
- overly censored IMO

and the others don't have enough activity to warrant looking as far as I'm concerned.

I haven't checked DT in a while.  I managed a couple of times to get whatever moderate criticism I had removed faster than I could type it.  If they can't stand a tiny weeny bit of criticism I have no interest in that cleaned up version of reality presented there.

SS I check, mainly because the links to the most active ones are right there so it is tempting.  I actually like to read the Everything goes category - gives me a much better feel for the sentiments out there about certain controversial topics (e.g. political or religious) as going to political or religious forums where people of one particular believe system tend to aggregate and bash the poor guy/gal who happens by and voices a dissenting opinion.   That won't happen much anymore, though, as we were all reminded a short while ago not to be nasty and opinionated and keep it nice and civil and not say things that others might find offensive by any stretch of imagination.  It's going to get much more boring - but on the bright side: I won't be distracted by the latest post about Sarah P. and might finally finish that 100 page presentation for my client.

Also I have made around 800 posts on Microstockgroup and never had a sale. I'm a poor writer

I've had more sales through this site than I have or most probably will get on Yaymicro 

SS is the only one I spend much time in, but it isn't what it used to be. The politics and bickering has made it tedious. I hit the occassional pimp me thread, but not much else. On the other hand, I have a lot more time to process and upload images.

I have never understood why they let the certain people on those boards use it to troll for paying customers.  I can not even go to the critique forum any more it is painful to watch new comers being stalked

Very well put.

I check the forums at IS, DT and FT but rarely post. At IS I don't feel welcome there now as a non-exclusive and keep my opinions to myself. DT I will openly ask questions on the forums and give some advice back - same for FT.

The SS forums have become truly annoying of late and I don't bother even checking them anymore - it's all pimping and political threads.

For me, ISTOCKPHOTO -- VECTOR FORUM!

That place rocks. You can get away with anything, and nobody is out to get you. Really -- they have too much fun to really entertain anything negative. The moderation is awesome -- mostly Jenny Borton, and even if she has to knock down a thread for obvious reasons, its always in a nice and tactful way.

Of course, I used to think all the Istock forums were like this, but I find that a lot of the photographers can be pretty mean and sarcastic and the politics of the site are quite apparent (although I also know of some people who are very good at spreading cheer and a few you can count on for an honest critique without smashing your work).

For some reason, the vector forum is completely exempt to all of this!

Overall though I'd have to say Istock has it.

On that note, why don't you jump to my forum post here and show us your workstation!

http://www.istockphoto.com/forum_messages.php?threadid=76139&page=1

I mostly stick to MSG, although I'll pop into SS once in a while to see how friends are doing.  There's a fairly large group of us in California who get together a couple of times a year for a weekend of shooting, and SS is considered home base. 

The only time I visit IS is if I need an answer to a question on technique or post processing.  For some reason, I find more answers there than anywhere else.