While I was at Play N' Trade this weekend, I was introduced to the Retro-Duo by Retro Bit. The salesperson told me I could play NES and SNES games on the console. WHA'?! And avoid the flashing grey screen of death common with most NES (or the constant resetting, blowing into the cartridge, etc.) So I took a chance, and I bought it along with two NES games: Super Mario Bros. and Jeopardy.
It's very small...as in slightly larger than a VHS tape and works off standard RCA.
The only Con I have found thus far is that the buttons on the controller are incredibly tight so after playing for fifteen minutes, my fingers and fingertips hurt.
HOWEVER, that can be remedied by breaking in the controllers more OR (be impatient and) buy SNES controllers since they work off the same connection.
You just have to remember that the "AB" for NES games (like "Contra") are "YB" on the SNES/Retro-Duo controllers.
All in all...thus far...it was a good purchase.