I finally picked up a Retron5 a week ago and I'm really liking it. The controller sucks, but works OK for quite a few games. Save states are fantastic for making punishing games more tolerable, and for never having to enter a password ever again! And the upscaling is wonderful. These games look phenomenal on my TV.
The biggest reason I wanted one was so I could play retro games in my home theater. I've got a 720p projector that displays a 100" screen, and I've tried hooking consoles up via component and they look horrible. The Retron5 however looks gorgeous on that screen. Add in the sound system and it really breathes new life into many older games. Journey to Silius sounds amazing pumped through the R5 into my home theater sound system. I have to disagree with dashv that retro games shouldn't be viewed larger than 40". I played some Castlevania, Sonic 3 and Mega Man last night and watching those characters rendered at about 1 1/2 feet tall is awesome! I have a 40" LCD in my living room and they look wonderful on that screen as well.
I do have one main concern though. The connectors do grip the carts really tightly. I looked last night and a bunch of the pins in the NES slot are already bent, and I've been trying to be careful while using it. Its still loading games fine, but I'm worried that in two months its going to be too screwed up to read carts any longer. Anyone know if you can bend the pins back without taking the system apart, or should I just return the system for a replacement?