Re: FCP to Media Composer switch? Downsides?

"there must be a reason FCP built up a following"
You mean other than price? I'd love to finally hear one such reason. Really, I have found FCP to be extremely overhyped throughout its entire existence.

But OK, here's some thoughts:

Avid's effects handling, while sufficient for most, is not as flexible as FCP's.

FCP is resolution independent up to almost 4K, IRRC. With Avid, you get PAL, NTSC, 720p, 1080i and 1080p. Nothing more, nothing less, nothing in between.

Avid doesn't do XML. It does AAF, though.