Video editing for linux is evolving, so it is not mature yet, some professional tools are written in the rendering farms of Hollywood are very mature though, and very expensive (Maya, for instance is the least expensive going around 2000 grands), look what is Sheik, Lord of the Rings, Ice Age and many others are made of and you can tell. For amature video editing the best I've ever come across is kino http://freshmeat.net/projects/kino/?topic_id=256
But it is dodgy to compile.
P.S. here is a peice of the info dag among the debris of the net (google)
as it states there are no tools comparing to ease of use ULead and Adobe premier available on linux platform, I must correct it there are no free (free as in beer and often free as in speach as well) tool that compare to Adobe and UL. But we are getting there little by little.