I like using ATTiny and ATMegas on project. Easy to use and easy to hook things to. But it would be nice if they were a bit more powerful. I know there are cheap 32-bit chips, but I don't think you can put them on breadboards as they are surface mount.
I wonder why Atmel doesn't refresh their AVR line with beefier 8-bit chips with the same form factor?
For example, you could make an amazing sound chip with a 100Mhz ATTiny84.