I tried it out, I'm actually quite impressed which is saying alot b/c I've never really been a big fan of the ebay app most of the time I'd rather go to the full site.
Anyhow, this obviously isn't going to be something your going to be doing very detailed listings on or all your listings but if you store stuff at various locations and aren't always by all yoru stuff it can come in handy.
Today for example I was over at one of my rental hosues where I have some stuff in storage and decided to put up a few listings for items. Because I had my phone on me I could do a brieff listing, add a short description and measurements which is handy since its a pain to write down measurements and then go home and post later.
Downsides of the app are obviously you cant type fast on a smart phone though the voice recognition feature helps out. The other downside is though they do have regular and html option for the actual listing space it would be a huge pain to be going backand forth between photo bucket and ebay on an android phone getting pics and html.
Overall though I was very happy with the app. It's not going to replace your computer for your listings but in a pinch it will help and its a handy way to put up a listing quickly.