I wouldnt avoid a movie simply because of one actor. The rest sometimes more than make up for it.
I don't tend to watch Steven Seagal movies anymore just because I find it sad that an old man tries to still be the action hero! Bruce Willis can still just about pull it off, but not Mr Seagal!
But normally, if I like the idea of a film, I will watch it regardless of who's in it.
Its just I don't normally like the idea of any Stephen Seagal's movies!