Video and sound quality
Video quality on a PMP is usually fine, because you're supplied with special software from the vendor, and detailed instructions on how to best encode your video content for that particular device. That said, sometimes the encoding process can be extremely difficult, with some players supporting a very specific combination of file formats and video resolutions. You should check to make sure the encoding and upload process is relatively simple.
The adage "try before you buy" also comes into play here. Although the resolution of video content might be fine, you want full motion playback to be smooth -- so check for any skipping of frames, jittering, flashing or any other forms of artefacts.
Similarly, not all MP3 players have equal sound quality! As you'll read a little further on, quality can be aided greatly by better headphones than the ones normally supplied, but also look out for the signal-to-noise ratio (SNR) specification. You'll want a device with an SNR of at least 85 -- but a figure in the high 90's or low 100's is even more desirable.
There's not much point having a high-fidelity digital audio device if you're listening to it with awful headphones or earphones. Bundled headphones are often lousy, in which case add the cost of a good pair to your budget.
Some headphones come with remote controls built into the cable. If this is the case, make sure the sound quality is up to your standards or else you may be stuck without a remote if you have to buy a new pair.
If you are prone to getting tangled up in cables, you might also want to check out players that come embedded in a pair of headphones, so you can have "spaghetti-free" listening! Noise cancellation headphones (that block out ambient noise) have come down in price a fair bit recently and may also be worth considering -- but maybe not if you're jogging about the city and need to listen out for your safety.
Unless you're comfortable with scavenging the Net for the latest software for your new gadget -- and possibly forking out extra cash for it -- make sure you get some decent software with your player.
This applies especially to video conversion software that allows you to put movie files into a format that's perfect for your player.
Sometimes your computer may need drivers to recognise your PMP or special software to transfer files to it. It just depends on the device.
Many PMPs work simply with Media Player 10 or just let you use the Windows explorer to move files around on the player via "drag and drop" as though it was a standard external storage device.
Bonus features of specialised software might include playlist creation, file management and cataloguing, better-than-usual encoding and "transcoding" features (conversion between formats or compression settings), and the ability to download files from the player.
TV and radio tuners
Portable Media Players with built-in TV and radio tuners are great when you're travelling and want to get a feel for the local area and pick up some fresh content.
PMPs with external TV Tuners have been around for a while now, but have yet to really take off. If you come across models that include a TV tuner, check to see if it is digital or high-definition and if you can record from TV.
As mentioned, some PMPs have built-in FM radio tuners -- sorry AM talkback fans.
If you are looking at a player with a built-in radio tuner, look for memory presets so you're not left channel surfing manually.
PMPs with recording capabilities sometimes even let you record the radio to the flash memory as MP3 or WAV files.