I must admit, I was a tad dissapointed that we had to buy this thing in order to play some games for the N64.  Not that many require it, but the  best games DO require it to get the best performance out of it.  As the  days of Nintendo went by, so did the games and so did my endless day in the  house and not leaving it, to play with my N64.  I've come to the  realization that the PAK does help out much with many games that don't even  require it.  A fact that you might not know about the expansion pak is that  it does, in fact, help every N64 game out there, however, not all of them  take in the dramatic effect that it has to offer.  Games not designed for  it, won't use it as much or as well as games that do work with it will,  however, little things can be improved.  As with the N64 Expansion Pak,  I've noticed that many games (designed for it) work more than well on the  system and are greatly improved.  As the fact that Nintendo is pushing out  games that now require it (Majora's Mask, DK64)it is vital to have it.  A  tad pricey, yes, but beneficial all the same.