So far, I upgraded to “the best operating system ever” and have been struck by surprise: Logic Pro 9 didn’t see my 32-bit plugins I couldn’t live without.
Whilst the most of LP9 users thought that this is “a new feature” of Mavericks (by analogy with Logic Pro X or due to compatibility issues of 32-bit AU bridge with the new system), I tried the following:
1. Removed com.apple.audiounits.cache from /Users/chatski/Library/Caches, where ‘chatski’ is my username.
2. Switched Logic Pro 9 to 32-bit (Applications -> Logic Pro 9 -> Get info);
3. Launched LP9 and let it scan my AUs. Quitted Logic;
4. Switched Logic Pro 9 to 64-bit by unticking 32-bit mode in properties of the app;
5. Launched LP one more time and, again, let it count my AUs;
6. Launched my old LP session with my beloved 32-bit plugins and uncorked the champagne.