DV streams have pretty much become the standard for camcorder-based video editing, so yes, FCP is perfectly happy with it.
To add to the confusion, there are different types of DV streams (type 1 and type 2), and while iMovie prefers one, FCP seems to prefer the other. So there's a bit of converting/rendering involved when you capture with one program and use in another. But, it's not that bad.
As for converting old footage from VHS or other sources, you have a few options:
1. Keep using your Canon camcorder (assuming it has pass-through ability, meaning you feed the VCR signal into your camera's AV-in port, and out it comes simultaneously through the DV-out port). If your camcorder didn't have this pass-through feature, then you could buy a camcorder that does...
2. Buy a dedicated DV deck, which would essentially be doing the same thing as option 1. Decks are expensive, and you might even be better off just buying a second camcorder for the exclusive use of logging/capturing/converting your footage (DV or otherwise), to save wear on your other camera.
3. Buy a standalone AV-to-DV conversion box, like the ADS Technologies' A/V Link box. These have standard A/V inputs on one side, and a Firewire out on the other side.
edit: dwishbone, does the eyeTV box record (or transcode) natively to DV, or is there a conversion process that has to happen after the video is captured? Being a USB box I suspect the latter, but I could be wrong. I couldn't see anything about capturing to DV on the elgato website.
