The Express Passes aren't too bad...you can get 1 pass per Park Ticket at a time and have to wait until the time expires or you use your pass up before you can get another one. Usually what my parents and I do is get passes for each of our tickets, go on another ride (in the regular line) while waiting for the time we can go on comes. It may seem like more trouble than anything, but it works well if you don't have a room key from one of the Universal Hotels (I'm trying to FOTL with a room key for the first time this weekend, but I have been pretty satisfied with the regular Express Passes up until now).
The only problem is that Express Passes run out. For most popular rides (Spiderman and Hulk at ioA, MIB and Back to the Future at Universal) they run out around lunch time or a little after. So get the passes for your favorite rides...ASAP or you risk not getting any.
I'm curious about buying Express Passes too, but it sounds like the booklets are expensive and you only get enough for one person for each ride. Not bad if you are going alone I'm sure. But you can get Express Passes for free anyways.
Hope this helped!
PS - here's a trick that worked for me and a friend...flirt with a worker who takes the Express tickets! Yes, I said flirt! My friend and I did this for one guy and the guy used his walkie-talkie (we used express passes 2 times in a row and then hung out around him saying we were hoping someone would give us THEIR passes) and someone came up to us and took us to the FOTL...even in front of the Express Holders!!

Dunno if we'll ever pull it off again, but, it did once!!