Wow - I always maintained that I'd never extend VGA feeds over cat5 cable. I've tried maybe a dozen units over the last few years and they always seem adequate for a sys op to dive in and do five minutes on the server (creating an account etc.) but never good enough to drive monitors at hi-res that someone has to look at all day (in an edit suite for example). They all look smeary and soft.
Scene Double have a range that works splendidly - they use skew compensation (and in fact you get a whole host of LF and HF adjustments) to make the picture spot on - even at 1280x1024 over 50m of cable. I'm a believer! (I've just installed eight sets - they ain't cheap though - £899 a set).