Well, in fact I have it since Friday, (because they don't open stores on Sundays in France) and all I can say is that this console is quite good.
The main problem I had with it is that it has crashed once (because I was trying to connect to internet while running with a lot of stuff in my hands and I accidentally screwed it up by closing it so it freezed and I couldn't switch it off...) but it got better when I depleted the battery and waitng an hour and a half... it works now.
The console is quite good to handle, there is no more fingerprints to make on it and the buttons are nicer to use (compared to the DS Lite).I didn't found any huge difference with the sound quality of the other DS but it is quite good when we listen to music (AAC format, I know...)
The eyes of the DSi were the biggest surpise: the picture quality isn't too bad, though the level of detail goes prehistoric when we want to take pictures of objects that are too far. The face recognition is a mixed bag: it only works when there is a good light outside or that your face is in the good angle (it is really hard to do the ressemblance test, I had to struggle 5 minutes to make it recognise 2 faces).
The DSiWare is quite good. For now it gives us 1000 points to spend on whatever you like and the prsentation of the shop is nice (the downloading screen is cute ) but I think it will be a bit of a mess to find the software you want because it only shows 2 items at a time.
The good news is that I can play my Rhythm Tengoku Gold on my DSi, the bad news is that I can't play Rhythm Tengoku On my DSi which is quite frutrating and it means that I should take with me my DS Tank or Buy a GBMicro if I wnt to play it on a long travel ...
Besides of that Wario Ware Snapped is quite a fun game (when it works ...)