Bottom line: It's definitely sleeker, sexier and even more innovative than its DS precursor; whether that missing Game Boy Advance slot will mortally offend your inner old-school gamer depends chiefly on A) the size of your library of old Game Boy Advance cartridges and B) how intent you are on continuing to play and/or obsess on them, rather than moving forward with DSi-format and downloadable content. The DSi is definitely heavily slanted toward those who don't yet have a Nintendo handheld, and who want to play the newest games plus some modest additional audiovisual perks in a slick matte casing. You still have to do things Mario's way...but he's been doing this a long time, and is still awfully good at it.
+ Slightly larger dual screens
+ SD card support
+ DSi store downloads and decent browser
+ Sleeker, sexier matte casing
+ Protected power switch
+ Improved menu/game swapping
+ Twin cameras . . .
+/- . . . albeit modest, low-res ones
- No MP3s or imported JPEGs, Nintendo? WTF?
- Markedly reduced battery life
- GBA slot/support R.I.P.