First, I did find an excellent clarifying review that really helped me get a perspective on Riya's product/service, and also brings out some of the pros and cons of the Riya beta. It's Edward Baig's Personal Tech column in USA Today, from last week. Ed does a far better job than I could of giving an overview, and I recommend his column for those wanting to learn more.
Second, though, I will describe a few major flaws and minor irritations I've found:
1) When you do a search by name, there's apparently no way to match the mis-identified photos with the proper person, like you can in manual training mode.
2) I suggested via an email to Riya's tech support that they might want to make the "default" "Don't Know" rather than "Full Name", and it was suggested back (promptly I must say) that I really didn't understand the purpose of Riya, which is to identify friends and family members in your photos. Well...one characteristic of my photo collection is I have a lot of group shots, crowd shots, and even quite a collection of "portraits" I've captured for a couple of photo directory projects, so I have a very large number of "Don't Knows" and frankly, "Don't Cares". So it would really be an advantage for me to at least set the default for my account to "Don't Know".
3) I wanted to do an incremental upload of new photos from My Pictures and it started reloading my entire 10,000-plus photo collection, and I let it go, thinking it might correct itself, but no, it went through the whole nearly-two-day process again.
4) Related to topic #3, I haven't found a good way to get a simple "Windows Explorer" look at all my photos, in their respective file folders, etc. Maybe I'm missing something.