If you are a visually impaired person who wants a portable media player capable of playing MP3 files, content from Audible, DAISY books, protected music content such as that provided by Napster or Apple, and which is completely accessible to the point where speech prompts are provided to aid navigation, you are going to be disappointed. Such a player is not available.
In my view, if you want a player which comes close, the BookCourier and BookPort are very clear leaders in this regard. There are accessible and they are capable of playing almost all of the above mentioned content. The products are small, easy to use, well-made and you rarely find people parting with them once they have them. The disadvantage here is the storage capacity. This is quite limited and
there is an additional cost involved. Having said that, you could take the view that the "limited" storage capacity of even a 2 GB Compact Flash card is not an issue at all, since these devices are designed as a means of temporary (and not permanent) storage and as such you use them in conjunction with a computer. Therefore, the files will be replaced on a regular basis. I would attribute this point to the Milestone 311 also.
The Victor reader Stream however looks to be a very good contender.
Next comes the iRiver series of players with Rockbox installed. Using this partnership makes for an ideal combination, since a mainstream portable player is completely accessible with minimal adaptation. In addition, the storage capacity available is probably much more than the average person would need and from that point of view it would be difficult to outgrow the player. The disadvantages are that you cannot play protected music or spoken word content, including material in the Audible and DAISY formats unless you use a product like Sound Taxi to undertake the conversion. These players are now quite difficult to obtain and because of this fact alone, you may want to consider purchasing one of the iPod products and install Rockbox onto it. The limitations here are the same as the iRiver series with the possible added complication of hardware which is difficult to use. However, these players are popular in stores right now and are likely to be available for some time yet.
If you don't mind having all your files in a single directory, and want a product which is easy to use from a hardware perspective, the iPod Shuffle is a good contender. There are various limitations here depending upon what you want to hear, and be sure to consult the iPod page for in depth information.
The Zen Stone 1 GB product mentioned in these pages is ideal if you want to hear MP3 and Audible content. It does have the advantage of being able to move through books or folders (such as albums), but this player will not speak.