Part of the problem is that existing programs already perform photostream's function very well, so Apple has to do something different to distinguish itself, and because what's out there is so good, it's going to be very hard to beat what's out there.
The new Dropbox app on my iPhone allows me to select photos and upload them to my dropbox, which then instantly appears both in a folder on my desktop and creates a URL to a photoalbum. Individual photos can be excluded or deleted in the process. I work directly with the files rather than having to go through iPhoto and then export them. Photostream is a seriously inferior product in comparison. You'd almost think Dropbox developers were reading this thread.
That being said, iCloud in general isn't a bad idea and works well. I love being on my computer, downloading an app using iTunes, and then seeing it appear on my iPhone and iPad pretty much right away. I liked how it worked with Pages and Numbers on my iPad too. I can't quite get it to do the same thing on my MacBook Pro, though -- like it won't sync with Pages on my laptop.