The scopes that BEAST provides use a lot of CPU. An example is that while I am playing "passive.bse" with my desktop computer it uses about 60% CPU when scopes are enabled, and about 15% without scopes (and without meters).

When scopes are enabled, 25% are spent within the bse core thread and 20% within the GUI thread (thats the data the "Profiler View" window gives me), where as without scopes, the CPU usage in these two threads is neglectable (< 1%).

This performance was measured using recent CVS on an 64bit Athlon system, with the following processor:

stefan@lotrien:~$ cat /proc/cpuinfo 
...
model name      : AMD Athlon(tm) 64 Processor 3400+
stepping        : 10
cpu MHz         : 2202.916
cache size      : 1024 KB
...

Note: due to priorization, this problem should not limit the sounds that can be produced on a given machine with BEAST, as long as the suid wrapper is installed.