I have a Topfield PVR4000. While I am quite happy linking my SAT receiver, DVD Recorder, Computer, Stereo and TV, I have little to no knowledge of the innards of any of those.
Keeping that in mind, here are my 2p worth.
The PVR4000 has no interface worth speaking of to "download" the recorded broadcast to my computer. PVR5000 and upwards is better that way. I have linked the digital out of the Topfiled to the digital in-jack of my computer; persumably that is better than going by analog cable and re-digitalize again. As I don't know whether the broadcast format is converted to a different format when storing on the PVR internal disc, I prefer to record via the said digital link directly to my computer.
There is an extensive website (albeit in German) with Wiki and discussion on the Topfiled models in detail:
http://topfield.abock.de/