I'm surprised to not see any discussion of the randomness famine many Linux kernel powered systems are suffering from:
The kernel entropy pool is quite small (4kbits). It used to be possible to resize it without rebuilding the kernel and rebooting but the resize api had an exploitable vulnerablity so it was removed. Concurrently, concerns about the quality of the random data from most drivers resulted in their contributions from the pool being removed.
So on many non-desktop systems you ~only get the 100hz timer input and can't even stock up much randomness. With things like apache and ssh reading /dev/random by default this results in a lot of mysterious slowness for things like SSH logins.
I'm surprised that I haven't to be much interest or discussion in doing anything about this outside of virtualization (which has it only slightly worse than many systems).
Of course, it's usually not hard to replace random with urandom but for systems that do sometimes generate long term keys thats a bit less than ideal.