It's certainly a pretty large bit of kit, probably the height of an old VCR and longer.
I've not had any problems operating it though. The series link is pretty easy to use on the UPC system, when you record a programme that has additional parts it asks whether you just want to record that episode or them all. In all the ones I've set up (quite a few) it's never missed one and doesn't record the repeats (for example 24 was repeated through the week on Sky, but the DVR only record the Sunday episode(s)).
The only problems I have experienced when there's a break in the series as it doesn't always pick up when it restarts if it's a long break. I think this might be more an issue with Sky and how they provide information for the EPG. I've never had a problem with the BBC series like Top Gear where I haven't changed or adjusted the record series setting for two years and it only records new episodes and it automatically starts again for the new season. It's only the occasional programme on sky. It's not a deal breaker, just a matter of being aware when it restarts and resetting the recording.
The other issues are really around scheduling, tweaking the start and end times as it isn't automatic. That's the biggest pain, especially if you're recording one programme after another and the first overruns. This problem is limited mainly to the BBC in my experience, I don't think they have quite the same sticking to schedules as the commercial channels.
The menu's ok, but not always logical to me. But really it's not that bad.