Okay, for those who are interested, I've spent a while in John Lewis today where they have both the Digital Stream and Philips boxes on display. John Lewis in Kingston was where I got the demo done but they had no stock of the Philips so I then traversed London to the Oxford Street branch where they had 9 in stock (so 8 or less now).
After a little play with them both, the Digital Stream definitely had a better feel to it (except for the annoyingly slow performance of the buttons). This was mainly in terms of still being able to see the programme transparently in the background and hear the audio when in EPG mode, whereas on the Philips, you lose the programme you were watching completely and can only see the EPG. Even more annoyingly, on the Philips, you can't directly access a channel from the EPG, you can only set recordings. To access a channel, you have to exit the EPG, then either type in the number of the channel (if you know it) or press OK and then scroll to the channel you want - naturally this menu doesn't show you what's actually on. Very silly! I've read elsewhere that Philips / Pace are listening out to the complaints of the current box and will look to sort them out via firmware upgrades, so with any luck, this will be fixed sooner rather than later.
Both boxes worked well in terms of recording, I set up a couple of recordings on both (the news) and they both started and finished without cutting out any of the programme.
However, after a little effort I managed to get them to also hook both the Digital Stream and Philips boxes to the same TV so we could do a comparison of picture quality (this was after the "expert" came over to help and told me they'd look identical - yeah right!). Without question the Philips produced a sharper image on both the HD and SD channels. And that's why I came home with the Philips
Got to set it all up yet now, so will report back later on how it all looks!