Our sincerest apologies for the slowdown during today's spike in activity. To give you an overview of the problem, our trade-engine code executes trades in under 20ms, however the Bitcoin-bound code takes 10x-30x longer to settle the trade. Bitcoin client is still in beta at version 0.8, so putting heavy, real-time load through it is the performance bottleneck. All Bitcoin start-ups are struggling around the same issue. Several Bitcoin websites use a detached/decoupled architecture to work around the problem, while we have decided to take a different approach and fix the root cause.
That doesn't make any sense at all. The performance of your trade engine should have nothing to do with bitcoind, because there's no reason that internal database adjustment to customer balances have anything whatsoever to do with the blockchain, and even if it did that doesn't explain why every action on the website is sluggish even on the best days.