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.  Other 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.