DSi is sort-of usless and not needed. A ripoff? Nah, I guess Nintendo just wants more money. Honestly, i dont plan on getting a DSi mainly due to the fact that I have a working (atm) DS Lite and getting a DSi would be pointless for me, along with the fact that I love Pokemon and couldn't live without the GBA Slot (I was annoyed when I found out the regular DS couldn't play GB and GBC games so...I even bought a new SP!)
Even with the addition of a camera etc, losing the GBA slot is horrible! (Especially if you own GBA games and dont have a GBA, GBA SP, GBA Micro, Gamecube w/gameboy Player.)
I wouldn't call it a rip off, if you love the new features and dont mind losing the GBA Port.