Generally speaking, 3rd party hardware for video game consoles cannot gain a foothold if the product is not either innovative, or priced competitively. This Mad Catz Expansion Pak is neither.
Recommend this product?
A look at what this expansion pack is supposed to do: The Expansion Pack is going to be plugged into the heart of your N64 and you do NOT want to stick anything cheap into there, or else you're going to fry your N. If the expansion pack does not work, you won't be able to even run a game on your N64. It's supposed to increase the Ram of your N64 to 8MB, and provide higher resolution graphics. With this sort of hardware, it either WORKS, or it DOESN'T. There is no in between. It's not like a controller or rumble pack. If this part of your N64 does not work, you will NOT be able to play ANY games, and if since it's plugged right into the middle of your N64, it can do a lot of damage if it's not made properly.
That is why it would be wise to research ANY 3rd party expansion pack (which is what you're doing right now if you're reading this review). Nintendo's version of the expansion pack generally costs 29.99. This expansion pack sells for 24.99. From my experience, there is absolutely NO DIFFERENCE between the two in performance. It allows the same features as Nintendo's official expansion pack does, and so far it has done NO damage to my N64 and has NEVER locked up during a game. However, you sacrifice peace of mind for a mere $5. Nintendo will not fix your N64 for free if you mess it up using un-licensed 3rd party products. The choice is yours.