I know people who game on both Vodafone RBI and Skinny's 4G service and it is fine (where fine being - with a stable signal strength you shouldn't notice any issues).
Depends on game really...
anything should work, but if it's deemed as unplayable is another question.
Anything hosted past AU your probably used to any sort of delay and never going to notice it.
Any comments made are personal opinion and do not reflect directly on the position my current or past employers may have.
Depending on the game, it's going to range from "not great but playable" to "OMFG this in unusable".
Source: I used Skinny 4G for a month or so while waiting for UFB last year, and I'm a heavy gamer.
Just like above depends on what game.
I can play WoW on my 2.6Mbps DSL line with ok latency (47ms)
My Spark 4G router gets 29Mbps and much lower latency (23ms in most cases) (just have to ensure that my updates are turned off or I chew through data!)
The stability of this will depend greatly on location though so what works for me may not for you!