Multiple Quotes in a reply. (Multi-quote capability) Either a UI Button in the Reply options to format an embedded quote or "multiquote" option buttons beside each post, so they can be toggled to be added to the reply when it's created.

Variable size composition window for replies. (A little window drag-sizer icon at the lower-right corner of the window.)

Non-volatile memory for the reply window. I just had to retype this because I clicked on the "Full Page" option and back-paged to return to this window and it dumped everything I had written. :)

Would automatically interpreted hotlinks be too much to ask? (ie: Pasted raw links) Or, is the forum going to be blocking all html commands?

Please take the Forum Monster out back, behind the office, and shoot it in the head - It likes to eat my posts... :)

Auto-refreshing after Reply, so I can see my reply in the thread so I don't have to actually click on the thread's link in order to force a refresh.

A "Do Art More Better" button beside each post, so I can re-render the posted render in order to make it look more betterer... ;)

A "Thank You, You're Awesome" button that appears besides any BagginsBill post, so I can click it, lots. (Seriously.)