My experience has been that Slacker song loading is faster, and map tiles draw faster, but the real benefit has been that coverage is much better with the LTE module. I get connectivity in areas where I never received it before (zero service turned into 3-4 bars LTE).
You do not get hotspot functionality (although now that all the other manufacturers are adding it, perhaps Tesla will go to offer that).
And no, the browser is not any faster. It's still the same slow,broken-down beast it has always been, running javascript through a real-speed TRS-80 emulator.