Although this does look pretty cool, all in it's a bit expensive. However, that being said...
I dig it. I have a pretty good collection of PS1/Sega CD games, and have been thinking about getting some more Saturn discs (but I don't have a working Saturn sadly). If they can really pull off a playable Saturn experience, I'd probably buy in just for that... But only if I can buy the base unit and the CD attachment only.
I've already got a RetroN 5 for my Famicom/NES/SNES/Genesis cartridges, and that's been good to me so far (despite the reviews on the early models).
For my GC/GBA collection, nothing beats the Cube with the Gameboy Advance Player (although the RetroN plays GBA too, I've never used it).
I have an n64, but if you ask me it just doesn't hold up well and I have little to no interest to buy carts for it. The 15 or so I have are more than enough.
Don't need too much more than that.
Although I agree with @hansolo77, the Pi is a decent piece of kit... Sometimes you just wanna experience the console feeling.