What's new in 6.0beta1 (2012-Apr-13 15:26):

*) updated drivers and kernel (to linux-2.6.38.2);
*) improved interface management (scales well for up to thousands of interfaces and more);
*) improved queue management (/queue simple and /queue tree) - easily handles tens
   of thousands of queues;
*) improved overall router performance when simple queues are used -
   at least double the performance of v5, even bigger improvements on multicore systems;
*) very small overhead for packets that miss simple queues,
   but simple queues are present in the system;
*) pcq queue is NAT aware (just like "/queue simple" and "/ip traffic-flow";
*) in "/ip firewall mangle" can specify "new-priority=from-dscp-high-3-bits";
*) new default queue types: pcq-download-default and pcq-upload-default;
*) simple queues have separate priority setting for download/upload/total;
*) slave flag shows up for interfaces that are in bridge,bonding or switch group;
*) global-in, global-out, global-total parent in /queue tree is
   replaced with global that is equivalent to global-total in v5;
*) simple queues happen in different place - at the very end of
   postrouting and local-in chains;
*) simple queues target-addresses and interface parameters are joined into one 
   target parameter, now supports multiple interfaces match for one queue;
*) simple queues dst-address parameter is changed to dst and now supports
   destination interface matching;
*) dns cache logs requests to topics "dns" and "packet";