I'm not sure why, but ARIKA had really problems with their DSi game Metal Torrent. It lags on a DSi, although it uses DSi mode there.
It's one of the coolest games on earth, but it lags... It's unbelievable.
I love this game.
Wut? Where? Who? Is this on european DSi store as well? Cause 3DS has select DSiware titles and I so want to play this. Must look... nope, at least not on 3DS´s estore.
And slowdowns aren´t uncommon in bullet hell shmup. If anything it makes it easier to navigate the patterns, if input is still consistent, that is.
The eShop has all DSi games available, just search the name of the one you're looking for in that search thing at the bottom (or wherever it is again, I forgot and can't be bothered to look).
Also, this looks great, although it still doesn't convince me into buying an iPad. I'd much rather see this released on Android.