Well, I did it, I bravely entered an Apple store today
Me: "Where's your Mac Pro, I want to try Final Cut Pro"
Dude: "Over there Sir"
Me: "No, that's the notebook, I want the desktop"
Dude: "Oh, I think we might have one right over there in the back"
Me: "Ok, so how do I use Final Cut Pro"
Dude: "What's that?"
Me: "It's video editing software"
Dude: "I'll have to see if a technology training specialist can help you with that."
Me: "Ok, thanks. I'll have a go myself while I wait. Now, how do I copy these files from my USB stick to the hard drive"
Dude: "You just drag and drop"
Me: "I can't use a copy command?"
Dude: "I have no idea, you just drag and drop"
New specialist dude arrives.
Dude: "I highly recommend you don't get the Mac Pro desktop"
Dude: "It hasn't been updated in a long time, and it's just not recommended as a new system"
Me: "But I need to install a PCI accelerator card"
Dude: (has actually heard of the matrox card, impressive) "Ah, ok, that's the only reason you'd want one.
Me: "So how do a I copy these .MTS video files from my camera into Final Cut"
Dude: "You can't do that, it has be in the original card format"
Me: "You're kidding right? I can't just copy and drop a .MTS file onto the timeline"
Dude: "Nope, it's always been that way, it's silly"
Me: "That's almost a show stopper. How about this .MP4 file?"
and to cut it short, the MP4 file worked, Final Cut Pro edited stuff like I expected it to, and Compressor did seem to have a Constant Quality H.264 render option.
So we started rendering my 10 minute H.264 MP4 file (with no edits, just a single clip on the timeline) with same specs as the input file and default "High" for constant quality setting. And we watched the progress bar creep up and up I gave up at the 30 min mark when it still wasn't half way, and it said 39min left.
Me: "This is your top of the line Mac Pro right?"
Dude: "Yep, fully optioned up"
Me: "Is it always this slow to render"?
No wonder the Matrox CompressHD card boasts that it takes Final Cut Pro up to "real time" rendering, it had bloody well want to!
For reference, to render and transcode the same 10 minute video on my current system, would take <20min total, for both steps in the process.
And I have a nothing special i7 notebook.
So it looks like, at best, a $3000+ Mac Pro with $330 Final Cut pro and a $500 Compress HD card would probably come out the same speed as a relatively high power cheap i7 system running $80 Vegas + free Handbrake.
Sorry sorry all you Mac and FinalCut Pro fanboys.