I've got a Samsung S7800. I don't think I've ever been in the position that there were 3 things on telly at the same time that are worth recording. Ever. So I can't answer your question, but this may be useful info for you... Previously I had a Humax freesat Foxsat HD (non-PVR HD Box) and in terms of a user interface, it was much better than the Samsung. Some observations:
• the Samsung's on screen "i" button takes up a LOT more of the screen than the Humax - so lots of the picture is obscure. The info screen is also poorly laid out, with lots of redundant space and pointless info showing;
• when the "i" button info on the Humax you press once to get the info up, a second time to give more detailed info and a third time to clear the screen. On the Samsung, once gets the info (see above), a second time gets the expanded info (which could probably fit into the first level of "i" if they properly laid it out, and a third time gets a signal strength screen – which is totally pointless here, it's rare day that you really need to know your signal strength and quality are 80% and 100% respectively. A fourth press is required to get back to the picture. (I realise you can press "exit" at any stage, but to be honest, it's neater to not have to look around for a different button.)
• HDD is quite noisy – this is probably a feature of most PVRs, but it's behind a glass door (admittedly in an open-back cabinet). I can't compare to the Humax PVR, but I find it annoying.
In general, it's a good machine, but I really preferred the user interface on the Humax.