Having an IQ of 130 or more seems to be the (approximate) bar you have to hop over to get in.
Is that about right?
Yes. 131 (sd of 15).
I can only share my experiences with the 'local' Mensa connected to the International Mensa (Mensa HungarIQa). Same rules, but the test is different, as I've read. There are two groups, sorted by Raven's Advanced Progressive Matrices:
1) 2% (131-135)
2) 1% (135+)
That means we never get to know our IQ accurately. I mean, Marilyn Vos Savant and myself would join the second category with a difference of approx. 80 points, which is kinda inconvenient, but understandable because of the small sample.
As for the real life experience: they're a nice and harmless geek group, mindfucking each other at least once a week around the dinner table. IRL they seemed to be really nice, but a little... well, INTP-ish. They were a lot more interested in games than myself.
Online, though - they are terrible. Always bashing each other, everyone knows everything best, and they seem to have an awful lot of free time with a dash of cloaked inferiority complex.
There are some advantages in joining - SIGHT (google it) and discounts in various shops ranging from 10-90%. That's it. At least for me, since I didn't feel too comfortable being around them.
The original goals of Mensa (schools, social initiatives etc.) have faded, and everything that's left is "a garbage heap run by a bunch of hedonistic fools". But this is strictly my own opinion, don't take it too seriously. I'm sure they think otherwise