I bought the SageTV bundle when I bought the PVR350. I actually liked TitanTV better. TitanTV isn't pretty compared to SageTV, but it displays A LOT more listings per page than SageTV did. I can't stand the TiVo look anyway.
A couple of things about TitanTV and PVR350. TitanTV scheduling feature doesn't work with FireFox ( probably an ActiveX thing ), so you'll need IE for that. You'll need to follow the instructions concerning WinTV Scheduler and Windows Task Scheduler service. Install the Hauppauge components in the order sugested on their site. If you have an Intel CPU with HyperThreading, you will need to disable HyperThreading in the BIOS. It seems that the WinTV software doesn't work well with HyperThreading and will result in program lockups / missed recordings.
Since I mainly record episodic TV, I just set up the weekly recording with the Scheduler and just use TitanTV to schedule / record select programs.
I'm not trying to knock GBPVR but it just looks like another TiVo clone. You can see that it only has a seven listing - 4 column time listing. My TitanTV page has a 19 station - 6 column time listing and is COLOR-CODED.
Before paying for SageTV or BeyondTV take a look at the TitanTV ( free ) sutff that came with your PVR350 package.
http://www.titantv.com