Well, I did it, ordered a 4-channel 200 MHz digital scope.
Might be overkill for Arduino work, but I certainly won't be under equipped.
http://www.tequipment.net/InstekGDS-2204A.html
Includes 4 probes. I like the ability to add modules later for functionality if, for example, my Saleae 8-channel logic analyzer proves ineffective with its 24 MHz sampling.