In summary, ReadyBoost probably won't improve your computer's performance much. If you have a very small amount of RAM (512 MB or so) and a very fast USB drive, you may see some increase in performance – but it isn't even guaranteed in this situation.

Does ReadyBoost really increase performance?

Really fast hard disks can often perform some, but not all, nonsequential read operations faster than a flash-based drive. In such cases, ReadyBoost won't provide as significant a performance gain as it would if your hard disk were slower.

Is there anything better than ReadyBoost?

The best alternative is PrimoCache. It's not free, so if you're looking for a free alternative, you could try SoftPerfect Cache Relocator or HDDTurbo. Other great apps like ReadyBoost are eBoostr (Paid), MaxVeloSSD (Paid), O&O CleverCache (Paid) and SuperCache (Paid).