I have, but some of them are restricted due to using a 32-bit version of Windows. Point is that they weren't suffering from errors on 1.4, but they are on 1.6. I tried reducing the view distance from 10 to 8 so that clients had to deal with fewer chunks, but this appears to cause a weird bug where the chunks in "rings" 9 and 10 around the player's spawning location never load. In other words, the player logs in, and all chunks within 8 chunks of distance load fine, but chunks 9 chunks away from the original spawn-in location don't get sent to client, nor chunks 10 chunks away, even when the player explores to them. Chunks beyond the 10th chunk load fine too. Resetting fixes the issue, but also reproduces it. Little annoying that players have to reset their connection to the server every time they travel 8 chunks.
I have having similar issues with with my 1.6 servers.
Try changing your chickenchunks.cfg
#The number of ticks to wait between attempting to unload orphaned chunks
cleanuptime=0
Setting this to zero immediately starting forcing the other chunks to load as players approached them.