1600x900, and when the truck pops up, it covers the bottom 1/4 of my window.
It's poping up on every refresh or foray into another thread.
It would be better if it were at least a new ad each time (or at least a cycle of a few), but the same guy popping up will get annoying. I don't have a problem with dealing with it for a while though, until the kinks are worked out. I think the graphic needs to be smaller for those like you using 800x600, so you can at least have the option of clicking it off. I agree that too much advertising has a negative effect, especially when it's so obtrusive.
I'm not really a fan of the bottom pop up banner either, because when I load the page and start to scroll down to look at new/updated threads, it bumps me back to the top when it pops up, though I haven't gotten that one so far since this new guy has been popping up.
Of course, I fully support whatever you have to do to keep the site operating, so long as it doesn't become a detriment to the quality of the site.
(He even popped up when I tried to post this, linking me over to Chevy's site - yeah...that's annoying...