I agree I don't miss types too much when the amount of code is small. However, when you have thousands of lines of code including code you didn't write and JavaScript spits out a "undefined is not a function" error in the middle of running a complex program, static typing can save you a huge amount of time and sanity.

Also, what are you losing by introducing strong types? Why wouldn't you want the compiler to verify the logic you're keeping track of manually?