The 7800 is worth it for three reasons:
Centipede
Robotron 2084
Homebrew
My god, the homebrew! If you like arcade classics, get that machine pronto. Then make sure you get it modded. I used
ElectronicSentimentalities with no problems. (The site never could load on my home computer, but was just fine loading on my phone. I blame TimeWarner.)
A couple things, though. You do not need a euro pad. Only a small number of games utilized a second button. They're not bad games (in fact, I recommend getting these 2-button games: Commando, Ninja Golf, and Midnight Mutants), but they're so few you can most likely get by without getting one, especially since the three I listed aren't cheap (compared to the rest of the 7800 library, that is).
If you like 2600 games, too, then definitely get yourself a nice Wico stick or Competition Pro, or if you wanna shell out money,
UberArcade's stick is a solid production and feels nice. For Robotron, you'll need a different setup, but rubber bands and two regular Pro Lines are usually sufficient.
And about the sound, yeah it's TIA, but some games have a POKEY chip inside of them that allows for even better than Famicom sound. Check out Ballblazer to hear it. Some homebrews have utilized it, but because it wasn't widely used in the carts (Atari was being cheap and decided against using it in the console) it's a bit rare. I believe AtariAge, though, is manufacturing soon a chip that imitates it, so we might see a boom in awesome sounding 7800 homebrews soon.
Hope this helps! I love my 7800, and you really can't do any better if you're a Centipede fan.