Don't forget that as RS485 is half duplex (can TX or RX but not at the same time) you also have to have your uC control The /RE and DE lines on the RS485 transeiver this means that it uses 1 more port on the uC than using a RS232 transeiver (unless you use external h/w to detect when you are sending data - defeats the purpose a bit though)

I use RS485 all the time with no major issues

For multimaster on the network I am writing some CD/CSMA code - basically a random delay if the bus is already busy, this will allow exceptions on the bus rather than the master having to poll all the units all the time, this should also give better utilisation of the bus as well. (this isn't working yet)

Marshall