The ATTiny seems rock solid, no problems so far.
They are a bit tricky to program, as they need an Arduino loaded with the appropriate code to act as a programming interface, and you have to remember to do the ‘burn bootloader’ stage to get the internal clock running at the correct rate.
Well worth the effort though.
I’ll post my code and some useful links in a while, busy doing some decorating at the moment!
Pete.