I just started using Microsoft Live Mesh after hearing about it from Joe Shirey.  For those not familiar with Live Mesh, you can read more here, here, and here.

I have to say that overall I am very impressed with the promise of these services from Microsoft.

That said, the user experience leaves something to be desired.  I will do a more thorough review once I have been using it for a few months to give people a better feel for what Mesh is doing.  I also hope to have some time to be able to play with the Developer SDK, but that is probably wishful thinking =]

I am using Vista with UAC and Microsoft One Care.  Here are the few issues that I ran into when installing and synchronizing my first folder:

Installation

• I had to turn off my Microsoft One Care firewall as the firewall wasn't allowing Mesh to install properly.  I even tried to allow the application access to the Internet, but the initial wait time for the firewall dialog and the UAC killed the installer even when I tried to run it again.  Tried this a couple times.  Had to just turn off the firewall and then re-run the installer.
• Mesh takes forever to start up immediately after installing.  I have a reasonably fast machine and it took a few minutes, so I wasn't sure if the installation was successful or if the firewall had screwed things up.  A dialog letting me know that it would take a while would be nice.  Microsoft is generally good about these things, so I imagine this level of usability is at the end of the list of things to do.

General Usability

• There are few/no cancel buttons on some of the dialogs.  I just had to wait for the web operation to time out (which took like a minute or two).  I had a modal dialog on my screen with no way to do anything to it.
• Mesh takes a while to get going.  Again, more feedback would be nice.
• Mesh doesn't provide detailed messages in terms of what has been synchronized.  It just tells you X folders and Y files were uploaded.  A little more detail (although hidden from the default UI) would be nice.

Overall, I think this technology has great promise, and I look forward to other good software+ services from Microsoft (the Microsoft marketing people are in my head and I can't get them out!).