So this happened: http://forum.xda-developers.com/show....php?t=1987032
The author afirms the pool of random numbers is too small and when it gets empty it blocks the kernel, producing general lag. Apparently if the pool is increased the lag disappears and Android runs much more smooth. He has published an application that solves the issue.
Now, I dont know if its true or not, I have not tried it yet, but a lot of people in forums are reporting positive results. There is a way to do it without the app (that requires root), just modifying some parameters in the kernel. Its in the same thread.
If this ends up being true, as it looks like, this is a BIG f*** up by the Google engineers. That some random programmer on the internet managed to debug and find this bottleneck while Android engineers had not is embarassing to say the least. Also, this is why open source is great.