You should be fine, but just to know for sure, you can find raw MP4 files uploaded by Sanyo owners on the net. Those Sanyo owners are really cool!
Plus, be aware that QuickTime handles H.264 performance issues very gracefully (no doubt, as a design decision due to H.264's relatively heavy requirements). QuickTime's playback codec is made in such a way as to drop frames between i-frames (keyframes) whenever CPU usage gets too high; let's say you can only do 30fps, then the first thing you'll notice when you get a video with 50fps is that it will attempt to play back 25fps and that looks quite good, since it's an even 2:1 cadence.
It was this very feature in QuickTime that convinced me to upgrade from Sanyo's HD1 to the HD1000. The HD1 didn't use H.264 (it had the older ASP-style MPEG-4) and the HD1000 was the first to use H.264, and I use it for the 720p60 mode. I actually was in the position you're in, and downloaded some clips off the net, and to my delight they played *BETTER* than the 720p30 clips I was making with the old HD1. This is on my Dual 1GHz G4. That's when I was sold!
CK.
