OP, I doubt your suggestions are going to get the attention of Theymos, but I happen to agree with you about the search delay at least.  I have no idea why it takes that long to be able to search for something else or correct a mistake made in the search field.  That's been an annoyance to me quite a few times, and I don't have a clue why it is the way it is.

Regarding the 360 second restriction on posting: That's only for brand new members if I'm not mistaken, and it goes away very quickly once you hit Newbie status.  It might be a bit too long, since there are a lot of people who register on bitcointalk to post a scam accusation or get some quick info, and I can see how it's a huge pain in the ass.  The problem is that if there wasn't any type of restriction like that, there would be bots spamming the forum like you wouldn't believe.  Even with that 360 second thing, we still get problems from time to time with bot spam.

And yeah, a lot of things could be improved upon here.  The new forum software should fix all of that, and I hear it's going to be released any day now.