The most important thing to currently know about the Topfield TF5800 PVR/PVRt is that it is being discontinued in favour of the Topfield TF5810PVR.
The principle difference between the two is that the 5810 has an HDMI socket with HD upscaling.
If High Definition does not feature in your plans for a little while, then you currently have the possibility of buying one of the best Digital Terrestrial Receivers with inbuilt Personal (Hard Drive) Video Recorder at an exceptional price.
The Topfield TF5800 PVR/PVRt does everything that you would expect from a quality twin tuner DT PVR. Where it comes into its own is its software and USB link, which allows it to communicate with your computer in both directions. There is a strong user base and more details of how to use this facility can be found at http://www.toppy.org.uk/.
You do not however have to go this far. If you prefer your channels in a logical order say with BBC3 and BBC4 following BBC2, rather than in channel number order, then you can do this using the remote and various menu features. This is just one example of the flexibility of the Topfield range, rarely found elsewhere.
If you are looking at moving to High Definition then the Topfield TF5810PVR would be the DT PVR to go for