in short : yes it is kinda works

in long :
it is depend on what kind of your pc/laptop you have

if your pc have ssd, you don’t need the readyboost stuff anymore
if your pc harddisk is 7200rpm ++, you will barely able to notice the difference

but if your pc like mine

5400 rpm hard disk, 8 GB memory, then you may need readyboost

some people will say that if you have 8 GB memory, then you don’t need readyboost, that is not true, because readyboost will kick in when the system need to access your 5400 rpm hard disk (if it cached of course)

so, what kind of flash memory i use? i use 32 GB sandisk ultra and i put it on my internal memory card reader (27e at the time of this writing)

once i put it on my pc, i format it to NTFS and dedicate all the memory for readyboost

and just like any cache technology, you will get the benefit once the stuff that you want is cached

and just like any speed improvement psychology, you will feel the speed raised a little bit, but once you get used to it, you will hardly notice that improvement

and on my case, the speed improvement really feel-able when  i open lot of tabs on my internet explorer and opera then i play league of legends

then you know, i do that “alt+tab” thing to switch back to desktop,
the first time still slow, then the speed of switching back to desktop and back to league of legends is faster to near instant (even after i put my pc to sleep and close the league of legends)

so is it really worth it?
if you ever feel that your pc slow and you see your pc reading your hard disk like mad during that loading, then it’s worth it