This memory stick is wicked holds plenty of tunes and a suprising amount of movies too. I remember the days when i walked into Debenhams and they sold a 128mb! memory stick for £28.99 if they did that now people would think they were bein ripped off. The 4GB is by far the best value for money in my opinion and offers the best space for your money. I personally wouldent put 8GB's worth of music on my psp as its too much to search thru with the menu systems.
Loading times I cant realy notice the difference, but the gaming is the most improved i would say with the psp slim (2000 & 3000) as it uses the memory like RAM in your computer to load game details. This area is much improved with the extra speed but if you just use your psp for music and movies or you have the old system its not that much faster thn your current stick. That said at this price why not futreproof your memory so when you need the extra speed you can use it.