I'm in the same boat right now. We have two DS Lites and while I would like a DSi, I have no good reason to justify it quite yet. Once we start getting some DSi exclusives and/or some good DSiWare games, then I will probably take the plunge.

I agree if I had a DSLite I wouldn't upgrade either (except it's totally scratchy and half broken and stuff )
But I just had a NDS when it was released and sold it a few months later so I didn't have a DS for 4 years and therefore I preordered the DSi and got it just on the release date, and I think if you're going to buy your first DS or want to upgrade from the Original one you should go with the DSi (Except you're totally into GBA games )
But there are a few pretty good title announced for the DSiWare (Mighty Flip Champs, Pop+ solo etc.) And there are some good ones availlable now (eg. Dr.Mario and the ArtStyle Games and Realfootball 2009/Realsoccer 2009 which is a complete soccergame that could be sold for 30 bucks but instead it's only 8 $ an DSiWare ^^ )

I don't know much about technic stuff but couldn't the DSi Camera serve as an alternative to the gyrosensor? I think yes because in WarioWare Snapped it recognises your movements and it recognises how fast they are, too so I think the camera could be diverted from its intended use and made into a "gyro camera"