suggestions

The preview thingy is nice. And it would be even nicer if it would show (part of) the thread as well, so you can see the preview in its right context (and maybe someone else just posted while you were typing away).

(beter yet, ajaxfy it)

I do frequently find myself loading the thread in a new tab to refer back to it, so I'll come up with something better later, whether it be showing the thread on the reply page, replying on thread page with Ajax, etc.

Yeah, I found myself opening a new tab of the thread too :p

What if the thread is really long? Maybe put a limit to the previews? Last 20? Last 20 plus first?

yeah this is a good idea, if the forums get real active again then this will help, i often had to delete/edit posts back in the day when someone jumped the gun on me, screwing up my brilliant posts