If Polo won't commit to them, I will be finding another exchange and encouraging others to do the same.
Centralized exchanges have their role and finding another one may the right call for you, but either way I would still encourage trying to build liquidity on bitsqaure. I've had offers on there at times but I was often alone on the order book and didn't get any fills. I'll continue to list when I have the opportunity to do so.
How solid is the Bitsquare platform? Does it rely on "smart" contracts?
Very solid, I have made a few trades on it. You need to get used to the interface and the trade mechanic. No smart contracts...but it does use multisig.
How long until it supports advanced features like margin trading? That is probably a way out. It needs more developers.
Is there a testnet version to try out?There may be a test net version, but the main net works fine.
Once Bitsquare is somewhat comparable/competitive feature-wise, I'd be happy to offer some XMR there at a discount, to coax volume away from the morally hazardous exchange under the command of ETH Fed Chairman Vitalik "Helicopter" Buterin.
One other thing: You have to keep the app running to see offers and keep the app running to keep your own offer alive.
I copied it from github but I don't know how to run the application?
you can also build from source https://github.com/bitsquare/bitsquare/blob/master/doc/build.md but using deb package is by far easier. (always use trusted package of course)