My old external Hauppauge HD-PVR died over the weekend, so I've ordered a Colossus to replace it. I'll be using it with a Rogers SA4250, so I'll have to use component since Rogers uses HDCP, but that's no big deal.
I use Windows 7 Media Center, so I'm hoping the beta drivers work at least as well as the external HD-PVR drivers. I'm a little hopeful that I'll see a moderate improvement in the 5-6 second channel change time I was getting before. I use firewire for channel changes, so I thankfully don't have to worry about the IR blaster.
I like the idea of the Colossus because it will eliminate one of the external boxes in my setup, and I feel like an internal card is almost certain to be more stable and the external box. I'll post again when I've installed it and update on how well it works.