There were no packaged NPK files for 6.0b1 but I copied up all the individual files that were on my router (system -> packages).
Rebooted and ran a speed test. Looks great at 75 down / 5 up to my ISP. (I'm paying for 20 down / 2 up).
Wireless bridge to a 5.14 router works just fine. The new quickset graphs on the web page and on winbox are really handy.
We'll see how it runs after a few days. Anyone else have any comments?
edit: I went ahead and upgraded the other wireless without any issue.