Certainly not portable - but it was darn fun. Very difficult to keep the cartridge port in there - the Genesis 3 is even smaller than I remember. But I really wanted the fake cartridge (I think it was worth it)! I had given my son-in-law a Genesis USB hub build, but I really didn't want such a tiny box - I wanted something that was a little more substantial. I bought a 3 way back in the day (and a Nomad - two of them, actually). While I owned and enjoyed almost all the systems of my era (Mommy wouldn't buy me an Atari 2600, darn her - Had to do that myself later in life), I seemed to have the most connection with the Genesis - Somehow, it suited me.
My wish for a portable Pi? 6-button controller. Using the two shoulder buttons and the extra of the four face buttons is always awkward when playing Comix Zone....