My two pence...

There needs to be far more active moderation with infractions handed out for abusive posting, members should not be able to call each other "fucking cunts" for example, it makes for a very unfriendly atmosphere certainly for new users and it is completely unnecessary, there is no need to insult each other so why is it allowed?
There are also far too many threads that just turn into big arguments/slagging matches, I dont really know how you can stop that (aside from infractions for abusive posting as above), but it makes it difficult to have a 'nice' read through the forum when every thread turns to crap!
I spend most of my time in the RST room and TBH it's pretty good in there with most people trying to help each other out, but whenever I look into GD there is always some epic thread going on with people going crazy at each other.

As far as trading goes, I think that a 'one rule for all' should be in place, so your £10 a year fee allows you to buy and sell as much as you like whether you are a fully fledged business or a bedroom trader. It's all for the good of the community/members!