It has just about the worst ratings I've ever seen on an app from a big time developer, and those ratings are well deserved. On my iPad it launches, crashes, and then picks another app on my iPad to run. In my case it launches Photogene, another photo editing program. Huh?
For those lucky enough to get Photoshop Express running it crashes over and over. And over. Did anybody at Adobe test this thing? I'm sure it will be replaced by a working app at some time, but don't grab this thing unless you are really a masochist. It may be working fine for a few, but for most users the app is a steaming pile of frustration.
You've been warned.
Update: Several commenters note that launching the app in landscape mode may avoid the issues, which appear to be caused by PE trying to launch an introductory PDF the first time it's run.