We're building the best Bitcoin Exchange out there, and it will be fast and secure. We're really happy with our progress on the tech.
Tech however is only a small part of making a good exchange happen, and so right now we're spending considerable time in meetings. Not our most favorite way to spend time, but well worth it.
We don't have much time for social media and chatrooms right now, so the best way you can help right now is by letting people in other forums know that we're an active project and making steady progress.
Also: If you are or know someone with access to considerable Bitcoin Liquidity (early adopter or miner with 10k+ Coins monthly volume), we'd love to talk with you about what you'd want from a good exchange!
Further, if you have a friend in a Bank or Credit Union that is interested in Bitcoin - please put us in touch. We need more banks and credit unions who are willing to work with us. Your help might shape the future of Bitcoin!
To provide reliable persistence, we use a persistence mechanism similar to prevayler, which is also discussed in the LMAX exchange architecture. Every operation that changes a balance or the order book (or both) is recorded to a journal and live-replicated to multiple slave-servers ready for instant failover.
For any currency you don't want any floating point error. I suggest storing all math in integers denominated in the smallest unit (hundreths for USD/EUR and ten-millionths for crypto-currency(BTC/LTC/etc))