Re: Is it sustainable?
Tribes is F2P, I've not spent a penny on it and still manage to hold my own (most games)
I would agree that it's less pay-to-win than most of the F2P games out there, and I did play it for a while. Their pricing is also less insane than others - at launch it was £35 for pretty much all the content, which is much more reasonable (except that the game didn't have a whole lot of actual content - few maps, etc).
It was also the lack of complexity in the gameplay compared with the original Tribes games that put me off, if I'm honest. For example, they kept in all the weapons and armour sets that allow you to base-camp, but removed all the kit that let you defend against that. In the original I could build my own base, mod on the fly, etc, etc. Ascend is a poor imitation, as was Vengeance.
Still, the F2P bait-and-switch is there, if you ask me. I did far better in terms of scoring in the earlier games than in Ascend, and there always seems to be someone with a superior loadout ready to mess you up.