Been playing it since I got it this week at the Austin retro games fest.

Basically, you can play genesis, (master system with the converter), game boy, gbc, gba, NES, SNES and famicon on one system and through HDMI.  

I already had a sizable SNES collection, so really all I wanted to was stock up on some of the cheap games I remember having and playing (either owning, friend owning or renting at block buster).

First things first, if you get it, UPGRADE THE FIRMWARE.

I had it last night erase my Metroid Fusion (GBA) cart.  And I had most of the game beaten but not finished.

So yeah, it's a firmware thing apparently, did that pronto this morning.  

Also not a huge fan of the controller but it's convenient if you need wireless and an all in one controller for all game carts.  I wanted to get the original feel so I bought some genesis controllers (still have about 3 SNES ) and 1 NES (but not the square) controller.

This has been a nice break from the uber-realistic games we're all playing now.  1943 and Punch-Out still deliver

yes, for sure it's an investment, and yes ROMs are always easier.  But there's something about the popping in a cart, sitting in a gaming chair and playing with an authentic controller that (to me anyway) are better than ROMs.  This is more of a collectors toy, if you already have a large collection of carts, then I think it's worth it, the game coming through HDMI looks worlds better than the AV connectors.  Not to mention the cart's battery can be dead but you can still save locally on the retron, so an older cart that was basically useless without saves can be used again.