I've a video producer by choice and by trade. I edit on Avid at work and Magix Video ProX and sometimes Vegas for my side business. Just recently installed Mint on my laptop which I purchased to use as a teleprompter and figured I would "experiment" a bit. I had heard about Cinelerra a while back but have not had chance to test it out (this laptop won't cut it) It is the most professional looking, the others previously mentioned are more replacements for something like WMM, which is too basic for professional use. I mean you could use it, but there are functions you need that make the job faster and easier.
I've watched some video tuts on Cinelerra and it's functionality is there, as to whether or not it's stable enough that is another question. From what I can tell the developer created it for himself and releases updates when he finds something he needs it to do, but there is no a community version and Gravelbay it might be worth another trial. I'm just not sure how it well it would handle HD. I'm in the process of researching a new system and will probably trial either a dual boot with Win so I can use VPX and Vegas, and see how they run under Wine etc, but being new to Linux and not wanting to lose too much valuable time messing with things I might not. ( I'll make that decision when I have to).