- Being able to deploy an update for a program while the program is running, without shutting the process down. Your code-compile-debug-fix cycle is very, very

- Being able to deploy an update for a program while the program is running, without shutting the process down. Your code-compile-debug-fix cycle is very, very fast, so you end up very productive. - With threads, one thread can take the others down. With OS processes, it's hard to keep track of which ones are alive and available to send to. With (most) async programming models (e.g. Javascript, Tcl) you only end up utilising one CPU. With Ada-style async programming models you have to think hard about deadlocks and mutexes. The BEAM model solves all these problems.