I am using Lightworks, a professional NLE system. It has a steep learning curve and its own unintuitive, but potentially powerful, workflow*. But now that I am using Lightworks, I don't think I can turn back without missing the Lightworks way of doing things.
*I still haven't figured out what the 'workflow' is, but I know I will bask in the awe-inspiring beauty of it once I figure it out.
After trying out various programs...
I have ended up learning Lightworks. Although I haven't tried the others, I can say it has a steep learning curve.
Previously, it used to cost >$3000, I believe. But they have gone [or will go, to be pedantic] Open Source, for the most part. I don't know how it compares to other editors of the same grade, such as Avid, but nothing can compete with its new price tag. I don't think I would pay hundreds of dollars for Sony Vegas if I have Lightworks.
One feature I really liked was the curves for keyframes. Basically, you can add a curves for parameters like X position, or gain or contrast, and Lightworks will interpolate through the points. An extremely simple example would be panning from left to right or zooming in. You can add 'keyframes' for virtually any effect that has editable parameters (all of them).
I still haven't figured out the best way to insert clips or move multiple clips around/etc. If I use the 'easy method' to insert a clip in the middle of only one track, it gives me a indicator:
Current unjoined clips do not allow sync fixup.
...Which I haven't figured out.
[Edited by Muntoo, April 24]