here are some observations of 6.33.3 on RB532a. my own 50cents donation
very simple configuration here, eth1 goes to internet gateway, rest if's bridged , constituting local network . srcnat between them. wifi wmia-123ag(r) configured , however not used
as others mentioned before: system finishes booting maybe 3 times out of 10 power cycles, however if it goes properly then stopping of terminal communication might happen (from under winbox); didn't notice that with serial console yet.
i have experienced total hangs of whole system. sometimes just after rebooting, sometime after few hours
i use DNS service from localnetwork, with about 200 static definitions - mainly for blocking internet advertisements.
after some uptime, seems it is really random, situations happened where DNS service probably got hanged or crashed , and hostname resolutions became unavailable. i've noticed that winbox showed no previously defined static definitions then, and cached list was also empty. and also "servers" , "Dynamic servers" and "allow remote req" checkbox showed as service was totaly deconfigured
i wasn't able to login with winbox from time to time. before repowering all hardware
and finally pretty interesting observation i made - believe it's helpful. board has RTC set up by hand, i don't use SNTP
noticed that with 6.33.3 real time clock slows down ! quite much. didn't do precise estimation, but remember it drifts down a few hours per day.
maybe 6.33.x included some specific bug correlated with MIPS platform? some internal CPU timers, clock dividers are setup inappropriately. or any other evil thing was silently introduced with MIPS specific kernel hacks... i don't know.....
please, give any feedback if last info was useful for removing bug
right now downgraded to 6.32.3 and after 2 days uptime it works fine.
/edit: i forgot one thing yet, winbox dashboard likes to show 100% load when system becomes broken