Update (14 Apr 2012): Sometime near the beginning of August 2011, it appears that the Labs Edition no longer signs in to a Google account properly. People still interested in an alternative to the standard Talk client may want to take a look at Google Chat for Chrome.
Tonight I experienced an issue with installing the Labs Edition of Google Talk (Windows 7 32Bit). The installer downloaded just fine, but upon running it, it silently failed with no indication of a progress bar or error message. I thought I would take a look around before abandoning the idea completely. It looks like there are other people having the same issue as well, but neither the compatibility modes nor turning off my security software seemed to help.
Previously I had recommended to visit the direct download link of the msi file on the Google servers, but since then the Labs client has stopped funtioning properly (see update at the top of this post).