Actually, Remus, with AA on at anything much above screen resolution you won't get anything at all...it'll crash the program. I ALWAYS have AA switched off. If I need that extra quality, I export big and resize in Photoshop.
The answer to the original question is yes, people have exported stuff from SU that's fit to go on a billboard. Use Tiff or png...they use lossless compression...jpegs don't.
Actually, SU will export a tiff completely uncompressed...and it will be HUGE. You need to open it in Photoshop or something then resave it using LZW compression to bring it down to something reasonable.
If you do decide to use a jpg, make sure that the quality slider is at about 90%. You'll get some artifacting but it ought to be acceptable.