After several tickets with WG and some correspondence with Codeweavers, here is what I have learned about the issues with 9.15:
There are two new methods of starting the program--'Launch the game in safe mode' and "Launch the game with reset graphic setting' (click on the arrow next to that orange "Play" button. Either one of those may help get you into the Garage if you experience problems at login.
Regarding the hang after login ("Updating the Garage..." ad infinitum), try letting the connection time out, then re-connect.
I suggest a similar amount of patience if you experience a hang after a battle. I have experienced it, but it eventually loaded the battle results. Hanging when entering a battle and/or during the countdown is another problem altogether. I've not experienced it.
The white screen after CMD+tab to switch programs may still be around, I've not tried it since the first time I experienced it. I don't think the phenomenon will generate a backtrace report, though, because the only 'solution' is to force quit. If someone gets a backtrace from that, send it to CodeWeavers.
What I have not yet seen elsewhere is hanging in the Garage when loading the Emblems and Inscriptions menus. I've had that happen three times (the beta tester in me keeps wanting to poke at the sore spot to see if it still hurts). It looks like the program is sending calls to files that are not where they are supposed to be, or are not in the proper format (when clicking on "Inscriptions," I got parts of summer camo patterns and a hang (with backtrace report).
Regardless of what problems you experience, CMD+Tab out of WoT after a freeze and you should see a very ugly crash reporter (looks like a Windows 95 dialog box). View those details (it will take a few moments to generate the report), save those backtrace reports, and attach them to your tickets to WG (as well as CodeWeavers). When you click on "Close" in the crash reporter, both it and WoT will quit, and WoT may restart (I'm at about 50-50 on this). I never trust the stability of a program restart, though (MacOS 9 habit).
In an email from CodeWeavers I received this afternoon, the fix for many/most/all(?) of these issues is right around the corner. They have a working build for all the servers, but they are still experiencing some problems. If you give them ample information about the problems you are experiencing (and those backtraces), you may get a link to the latest build and a password to download it.
The alternative, of course, is to wait out this mess.
Good luck!