I've hit a problem with Gslapt under the alpha. Not every time, but frequently, if I use it to install a few packages at the same time, it does part of the job, then freezes and has to be killed.
Just happened a few minutes ago - I selected three packages (samba, ntp and wxGTK). The progress indicator got to the middle of installing wxGTK, then stopped. After 10 minutes, I killed Gslapt from the console. Turns out that only ntp had been installed, though both samba and wxGTK had been downloaded.
I had similar problems with the 5.9 Standard betas, but haven't seen it since then.