As many have mentioned, it holds about 30 minutes of music, unless you can find a memory card (I'm not sure if they are even made anymore, but I have seen them for sale) which will give you a whopping hour. If you're just going to use this for walking the dog around the block, or standing in line, or a quick run in the morning, this isn't such a big deal.
The USB-type cord is primitive and weird, so you'll probably be using the parallel port adapter, which isn't really a problem, but can be an inconvenience if you have a lot of things that use your parallel ports.
I'm pretty sure the company no longer supports this device or its software, since they have gone on to bigger and better things since its debut. Caveat emptor.
Also, it is not compatible with anything after Windows 98, but you can get around that easily by downloading the free program "Dreaming of Brazil" which works with XP, NT, and 2000. (Google search for "Diamond Rio mp3 player" or "Dreaming of Brazil.")
A few pointers from my humble experience with the Rio PMP300: If the headphones it comes with break, you can replace them with any headphones that fit the headphone jack. You should also take the battery out of the Rio when you aren't using it-- it sucks energy when it's idle. If you happen to need a little bit of misc. storage space, you can use the Dreaming of Brazil program to transfer any items that will fit, which can be handy.
I imagine this is not the best mp3 player you can buy, but if you can get it cheap, it's still a pretty good one. The main problem I have is the tiny amount of storage space and compatibility issues. Shop around for an iPod or a newer Rio or something if you're very concerned with absolute top quality.
