To start off I've shoved in a spare 20gb drive, which seems to be working fine; eventually I'll fit something bigger. Installation is dead easy - take off a plastic panel, plug in the drive cables, and slide the cover back on - no tools needed. Setup is also pretty easy and tuning is incredibly fast compared to previous freeview receivers I've used. So far the only downside I've noticed is that the programme guide colours are HORRIBLE and can't be changed. Reception is good, and everything seems to work the way it should.
I'll post more when I've tried recording a few things - so far it's looking good.
Later Rough estimate of capacity based on a short recording is about 16 hours on a 20gb hard disk.
A couple of other negative points - you get a red dot on the screen when you're recording. It doesn't go away. And there are no outputs for sound other than a digital phono socket - I had to use an adaptor to tap sound from the SCART lead for my amp since I'm using the digital phono on that for my DVD player.