Is there any way that you can monitor if ReadyBoost actually has an impact on performance? I don't really experience much improvement.
Also can it be useful for Visual Studio anyway or would that never help?
ReadyBoost is best noticable in start times of applications, given you don't use a SSD.
So, with ReadyBoost, Visual Studio should start faster once it's in the ReadyBoost cache.
It doesn't exactly give you metrics on how much of a performance gain you're getting, but on Windows 7 there is a set of performance counters (perfmon.exe) called "ReadyBoost Cache" that will at least let you know when ReadyBoost is actually doing something. I notice lots of read activity in the cache when building a solution.