I recieved this player as a christmas present, this year. I have been extremely pleased with it so far.
The MF-PD 100 is essentially the 360 model, without the remote or rechargable battery (both available to buy later). It has very few options on it:
Play, Stop, track change and volume.
So the remote which has everything else on is definately worth it, although getting it as a christmas present meant that I didnt have this option.
The player comes with 32mb of memory which is about enough for 30 mins of high quality music - not very much, but with the 2 slots you can upgrade easily (although memory cards seemed extremely overpriced at the monent, especially the MMC cards that this model takes). It is very small, perhaps the size of a couple of match boxes. Also it comes in a neat blue colour and looks rather cool.
The headphones that come with the player are outstanding, they seem to make the music play inside your head, rather than coming in through your ears. They are the best headphones I have ever seen supplied with a portable audio product.
The player runs for around 8 hours on 1 AA battery (6 with rechargeable), which is impressive and because of MP3 technology has no moving parts so can not skip.

This is the best value for money mp3 player around, if you are short on cash but still want one, this is it.