an improvement yes, but a huge one, no, relatively speaking anyhow... the largest improvement i found was in windows login times, and starting internet explorer (considering i did those enough to make a difference lol)... but, if you browse online alot (or anything else), it really can help, at least to alleviate slight annoyances in wait times, whenever they might happen... but for the most part, the things i mentioned did load quicker...
right now its in my brothers system (the flash drive is)... hes running vista rtm on only 512mb ram, lol... so, it definetly helped him there some