Yesterday I did the Windows Mobile 6.5 update for the T-Mobile Dash 3G
I was concerned that Skype for Windows Mobile would not work since on the website for Skype the system requirements are listed as "Windows Mobile 5.6 and 6.1"
On January 26 I tested the latest version of Skype for Windows Mobile on this upgraded phone with good results. At first it had a little trouble signing in but now it works fine, with no problems.
Also, I have successfully tested use of the phone for tethering via USB with our CradlePoint MBR 1000 Mobile Broadband Router. It seems to work fine with that and via USB with an Ubuntu 9.10 system as well.