That is rather unfortunate. Are there any better alternatives?
check out smallnetbuilder.com, they have some charts that show performance on various network storage.
The basic jist is that unless you spend $$$, performance tends to be pretty awful. You might be in luck since you are only connecting to the storage via wireless, so you might be able to find something relatively inexpensive that you can wire to your Uverse router and will be fast enough to saturate wireless. Besides performance, most of these devices offer more services than what you could get out of shareport.
The LG N2R1 might be something to look at (its not out until the fall), although there aren't any performance numbers for it yet.
I have enough computers that I added 3 1 TB hard drives to my Windows Media Center box and installed some free software called flexraid. Flexraid allows you to add any number of hard drives to create a simple parity raid. So I have 2 TB of effective storage, and if one of those drives dies, I can use the parity drive to recover my files. Performance is great too, since its just like accessing the hard drive and my media center is fast enough for handle the data transfer even when watching movies. This is probably overkill for you, but its something to consider if you can't find a cheap network storage and you have an extra computer sitting around.