One of my least favorite changes between the G1 and G2 is the relocation of the SD slot from the grip to the battery compartment. Yes, it's a very common location in point-and-shoots (and the Olympus models), but it's annoying if you use a tripod and awkward if you take the card out frequently.
Panasonic moved intelligent auto off the mode dial to make room for movie mode, which the G1 didn't have. You don't need to be in the mode in order to capture video, though, because the dedicated movie button works regardless of mode. You have a little bit of manual control during movie capture--a faux aperture adjustment setting called "peripheral defocus" and a limited ability to change shutter speeds--but it requires a slog through the manual to discover it.
Panasonic sort of swapped the locations of the Film Mode settings and the focus mode options; the former used to be on a button atop the camera and the latter on one of the four-way navigation buttons. I prefer this arrangement, as it reduces the prominence of the film modes. In addition to four different sizes of a single user-selectable focus area, there's also 23-area automatic selection, Dynamic tracking AF, and face-detection AF.
For the most part, Panasonic does a very good job integrating the direct-access controls and the touch screen adjustments. You can do almost everything both ways (except navigate the menus), and you can disable selective aspects of the touch-screen operation, such as Quick Menu operation.
The back dial on the G2 (it was on top in the G1) is a jog dial which most people would probably never figure out without reading the manual.
The G2 has a couple of user interfaces, though only one of them (top) can be used in conjunction with the LCD display (the other, on the next slide, works with the EVF). Like most cameras, the Q.Menu button lets you navigate around the edges of the display to change settings (middle). This works via touch as well.
While the touch-screen operation is pretty well-done, there's one infuriating, frustrating flaw. If you're in single-area AF mode and you touch the screen when it's not clear that you're going for one of the settings, the camera assumes you want to change your focus area and drops you into that interface (bottom), plus it moves the focus area to wherever you touched. You never realize how often you accidentally hit the screen until you've used this camera for an afternoon.
Despite the frustrations of the touch focus implementation, it's a nice feature to have. Even better, though, is the G2 allows you to directly access any of the settings. Many touch-screen cameras force you to scroll through settings via onscreen navigation arrows, but with the G2 you can simply directly choose the desired setting, the way a touch screen should function.