Tamron 200-500mm f/5-6.3

[JaceTheAce]

Does anyone here have any experience shooting motorsports with this lens? Seems like it'd be a good budget buy. Some people say it has lens creep and slow-focus issues. It looks pretty sharp according to what I see on Flickr.

[Cadwell]

I've never seen one at a race track. I've spent pretty much every weekend for the last several years at racetracks and I've seen most flavours of telephoto in use at some point or another. That might lead you to a conclusion.