I have this same combination and it works well - most of the time. Good quality pictures etc. and the guideplus is great too. No more manual naming of programs and no problems with widescreen/4:3 formats or switching.
I download the EPG data via ITV analogue (Can this be done through Eurosport on the STB - anyone know?).
The only problem I have is recording from some of the BBC channels, Cbeebies in particular, via the Sony STB - sometimes it changes the channel but displays the red screen and that is what records.
However, I think this is a function of the STB rather than the recorder as it does the same when changing channels with the STB remote. I just put another short recording in front of what I want to record and it sends the channel number twice which seems to get rid of the red screen.
Guideplus also seem to be a bit slow at adding extra channels listings. More4 and ITV4 listings are still missing and there is no indication of when and how they will be added (I am assuming they will be auto updated with the EPG download and appear one day) but you can still set a timer event manually. In this case it would have been handy to be able to programme a recording via the set top box, but this cannot be done with the Pioneer recorder.
Another function that is very handy is that you can add padding at the end of the recording very easily or adjust start and finsh times manually fairly easily too.
I do not have a VCR connected but there are composite and s-video connections on the front and rear (in and out) that could be used.