There is more info in the help about the SIM option if you look for it. There is even a mobile connection topic.
Looking at Virgin Mobile Canada's website they say their normal SIM cards are only H+ while the microSIMs are true 4G/LTE. I just wonder if RIM will give us some kind of upgrade path to a newer Playbook or will have to go out and spend another $600 on a 64GB... LOL
About facebook being smoother. It feels the same to me which reminds me that adobe air was supposed to be hardware accelerated at some point? Maybe not. Maybe I made that up Dx