Nice points Will !

If you plan to sell your games, I would also add:

Making a game is fun, but ensure player will have also fun playing your game !
Study the market and what's selling well on the games portal, you might be surprised.

Don't focus on a complex technical engine, focus on game design & contents
Handling 150k polygon scenes in realtime is great, but it does not make a game sell. In case you don't know it, the 2006 top selling casual game was a pure 2D game, made using ... Director.

Converge to a playable game
The main issue in an Indie game project is time. Focus on the essential, the core mechanic of the game, to have a playable thing as soon as possible. Then add features as required. As Will said, don't be too ambitious, focus on the strict minimum.