I quite like the 7800 but I have 2 issues with it. Firstly its the PAL version so I'm always thinking what the NTSC games would be like - its unlikely PAL games got any speed optimisation (can someone here shed any light on that?).
Secondly the video out really is its achilles heel in this day and age. I run mine through a VCR which helps a bit but the image still suffers from the RF output. I hear you can get mods done but they seem very fiddly and there's variable results.
Not really an issue for me but the lack of POKEY onboard hurts it too - weird decision that.
Really like the lineup - I have a small but enjoyable collection. My favourites are the oldies - the built-in Asteroids game is excellent and its rock hard too. Centipede, Joust and Food Fight would be my other favourites and I got the Pacman Collection homebrew cart from Atari Age which is the business though the PAL version's colour conversion means one of the ghosts is a bit hard to see but from looking at other games like Donkey Kong it seems to be an issue with some official PAL games too - some reds look like a bit washed out.
It being the PAL version it means I have the better NES style controllers so that's a plus though I don't use the little screw in joysticks - a mate broke one during a frenetic Demon Attack session anyhow...which brings me to the final plus - 2600 compatibility - hard to knock though I'm convinced 2600 games look better on the woody.
One more thing - the weird power adaptor connector? Bit of a worry that if it came to the point where I would need a replacement given the relative low numbers of 7800s.