I got DS about 3 weeks ago so i think i can help you.
1. DS Lite is the most popular one get that one is light, in nice colours, DSi is coming out next year so if you want it you have to wait.
2. Love RPG's? The World Ends With You, Final Fantasy IV, Etrian Odyssey 1&2, Final Fantasy 3,Final Fantasy III, Final Fantasy Tactics A2, Pokemon and much more coming. With Fire Emblem out in December.
3. Legend of Zelda Phantom Hourglass is a brilliant game for me better then GOW:Chains of Olympus (played both), depends thou what do you meet by Epic , Graphically DS does not come near GoW or CC on the PSP yet its library is amazing
4. Hard to say i havent played many games yet, but Zelda and FF IV look really good.
5. If you get DS Lite then yes you can use GBA, DSi gets rid of the slot but it will get some sort of avaliability to get games from DS ware shop.
6. DS does not have media capabilities so it does not really connect to many things. it's purely a gaming device.
7. Yes
8. Got it few weeks ago and it is able to go like 6-7 hours straight on highest settings.
9. Graphics are inferior to the PSP, and it's quite easy to break , but saying that it has amazing potential and games.
10. It's 99 Pounds in the Uk, and around 120$ in the US.
11. Loads of Games are cheap now, just look for occasions i've bout TWEWY for 15 Pounds and Zelda for 14.
12. DSi will surf the net, but DS is purely a gaming machine.
13. There will be memory cards for DSi
