I haven't tried it yet because the latest release is known as "Dracula" and i'm scared of it.
so all i can do is quote the front page i just linked to:
"what is it? : ChucK is a new (and developing) audio programming language for real-time synthesis, composition, performance, and now, analysis - fully supported on MacOS X, Windows, and Linux. ChucK presents a new time-based, concurrent programming model that's highly precise and expressive (we call this strongly-timed), as well as dynamic control rates, and the ability to add and modify code on-the-fly. In addition, ChucK supports MIDI, OSC, HID device, and multi-channel audio. It's fun and easy to learn, and offers composers, researchers, and performers a powerful programming tool for building and experimenting with complex audio synthesis/analysis programs, and real-time interactive control."
One of ChucK's raison d'etre is that it is "strongly timed". Considering the number of posts here about problems with Max's timing (rather than MSP, of course), there's a reason in itself to investigate ChucK.
It is a rapidly expanding language, with some very exciting recent additions. Many of them (analysis/resynthesis, for example) can be duplicated in Max/MSP with third party externals.
This summer Ge and company introduced sMIRk, a music information retrieval toolkit for ChucK. What that translates into for most of us is machine learning. The demo at ICMC and ISMIR involved giving it some audio data (piano music, then string music), giving it an opportunity to learn the difference (running the algorithm for a few seconds), then having it correctly identify new piano or string timbres, in realtime. It was a pretty sexy demo, to say the least.
This could possibly be done in MSP (using externals), but it's ready to go in ChucK/sMIRk.
Lastly, on the plane home from ISMIR, I was able to write a ChucK program (never having used ChucK before) that seamlessly talked to Max via OSC, using Max to send audio to ChucK, and getting (analysis) responses back, in realtime.
I am patiently waiting for Brad Garton's chuck~ external for Max 5.