I'll do my best to answer your questions and others might come behind me, or even before I finish posting this, to chime in as well.
1. Timeframe on v8. It's hard to say right now, but by the time new members area access would be expiring we'll definitely have a few updates put out. With a couple new developers, things are moving along quite nicely. It's a complete overhaul with an entire new look, so I'll be able to give out more info on some sort of timeframe hopefully fairly soon.
2. There will be an upgrade script to easily update your version 7.x forum to version 8. So no need to start with a clean install.
Creating your own themes and color schemes is fairly simple as long as you have a little knowledge of CSS. There is an editor in the control panel that allows you to change things and view your changes as they are done.
I can't really say on SMF, as I've never run one, but we're definitely seeing quite a few SMF converts in the past couple months.
I won't go into vBulettin. It appears to be some things going on over there, but I don't have a firm knowledge to really comment on it. Since I'm the lead developer on UBB.threads any opinion I could share on that would be entirely subjective as well
So I'll let someone else comment on that part.
