Linux has the super low end and the super high end well covered, but it has a few serious areas that are lacking.
On the low end, OpenShot definitely beats windows movie maker, and it's about as good as iMovie, so for vloggers, it's all you'd need.
On the high end, Lightworks and Cinelerra are both powerful, comparable to Avid, but less stable, and the learning curve is steep; too steep for an amateur who is just messing around to master quickly.
But for a start up or mid-range video production company, neither option is acceptable. OpenShot is simply not good enough for their needs, and the high end is too much, the training costs for employees would be significant. There is no Sony Vegas, Adobe Premiere, or Final Cut 7 for the mid range companies to work with.
I've also had trouble rendering to h.264 in Linux. The files are sometimes corrupt - refusing to load in anything other than VLC, sometimes lacking features, like progressive upload that is youtube friendly, or just plain poor quality - not all renderers are made equal, some look better at a given bit rate than others.