Hi,
I find a scope very useful, but you need to understand what it is showing you on the screen.. you can use it to quickly find audio signals on a board, to see if they are DC or AC coupled.. it will pinpoint clock oscillators, frequency dividers and a whole myriad of useful stuff..
A 20Mhz scope is fine for Circuit bending and 99.9% of them have a standard BNC connector for scope probes, although some probes have an attenuator built in giving a -10X signal on the screen in respect to what you are measuring.
Cheers
Paul