Very often leet speak is not realy faster. It just replaces characters for numbers....
When you realy go to sms talk as we say out here in the netherlands, you realy start replacing entire words. Makes life even harder, but it realy saves on characters.
if you know ten digit typing (fingers), normal typing is quicker as leet speak.
Personaly, I hate leet, as it is just another way to introduce a language barrier. Especialy for those that are not very strong in English.