The latest Version of the companion is 0.853:
http://imagemodserver.mine.nu/other/...atha/home.html
The companion is not buggy...
Using the Mod launcher is easier and better in many ways, I agree.
Using the RTC is not as good, distractions to the internet connection, the PBW server or the RTC client will cause SE4 to close aswell resulting in loss of data, this does NOT happen with the companion.
If a game can be started it will be started with the companion, if it doesn't start I bet your password is wrong.
DO NOT USE ANY OLDER VERSION THAN 0.853, check the CHECK FOR UPDATES box in the settings screen.