We both play with manual adjustments. Especially, with ISO, aperture, shutter speed, and compensation. We hardly touch the white balance.
My P&S is very noisy above ISO 200 and its flash is not powerful enough longer than 3 meters.
Outdoor pictures are good. I hate the lag between pressing the shutter and the actual snapshot.
When my daughter perform on stage we both are watching.
So me using the heavy gear is not a problem.
When my wife is alone she need a much lighter camera.
She wants to be able to use higher ISO.
To catch the moment and not miss it due to slow performance.
Take better video clips (SX100 IS capture 640 X 480 only).
Play with depth of field.
We do not use post processing and not planing to.
I guess jpeg quality is enough for my use.
On the other hand, i will probably want to try HDR in extreme light conditions.
It will never be more than a hobby.
However, my wife invest lots of time on this hobby.
After every trip abroad she use a photo album software and print the final album as a book (printed by professionals on a quality paper).
Three months ago a friend gave us his old Nikon D70 with 18-135 slow zoom.
The pictures were better than with our P&S.
However, it was too heavy for my wife and the lens did not offer a lot more.
I found Canon easier than Nikon.
However, if i have to choose one system, it probably would be a mirrorless Panasonic (I hope no one offended).
Currently, we take the camera everywhere and we do not plan to change that.
Sorry for not providing all answers on the first post.
The above information fills out a lot of gaps from the initial post. Lets evaluate this piece by piece by equipment:
Replacement P&S - S95 or a G12 if you go Canon. I've always been a fan of the G series and will probably consider the replacement when it comes out. However, the Panasonic Lumix is really where things shine for me. These cameras are underwater monsters, fast, light and everything you want from a P&S. Having a P&S is important, especially for birthday dinners, small functions and doing things that require light, small and less conspicuous cameras. I would go to the camera store and have a play with the three mentioned cameras, look at the flash capabilities, zoom ranges and the general ergonomics of the cameras and invest in what feels and looks the best to you. I usually bring down a 2mb SD and have a play with the P&S I'm considering with the salespeople. Of note, the G12 has an HDR mode which does jpeg post-processing for you and combines the image (HDR is possible from jpeg, but RAW is 800 times better) and will shoot RAW.
Mirrorless or Micro 4/3s - I personally don't care much for these systems as you tend to get better results from a DSLR. I'd agree with the suggestions prior, Panasonic or Olympus are the way to go from the test results. I wouldn't invest in a 4/3s and a DSLR though, that seems like a massive waste of money and energy, not to mention, the additional baggage. It becomes a question of what you're willing to sacrifice.
DSLR - With the information given, I'm a bit mixed about what to suggest here. Honestly, a small Rebel would suit your wife and your needs. The 600D is the way to go, or possibly wait for another few months and get a 650D when it arrives around 2nd quarter 2012. You should have a nice set of features including better ISO, noise control and 18 mega pixels of colourful goodness. If you had a desire to step further into the hole, possibly a 7D for you, and you alone. This is not a camera your wife would use, it is far too heavy and bulky and looks like a brick surrounded in black plastic and rubber. This would give you your manual settings controls and something to start collecting some nice lenses for.
Video Camera - Sony or Canon. Period. I don't like the Panasonics, but that's only because the controls are really difficult for me to handle and they seem to be made for men and men alone. I've previously shot with a new Sony, and it handled like a charm in low light. Stills were even decent enough to warrant a few retouches and presentation. Ergonomics were good and the camera was lightweight and didn't impede on my ability to have fun while filming.
Lenses, Post Processing and RAW v JPEG - Since neither of you have a desire to mess with things post facto, obviously you want to get the best images from the first time around, stick to jpeg (as mentioned before, it is possible to HDR jpegs even if it isn't as pretty) and skip the software. In my opinion, at least 50%-60% of my work is post processing simply due to time, however, it has fallen significantly with the addition of good lenses. So, this is where Neuro's suggestions of better lenses come into play. Better glass will give you better results the first time around. This doesn't mean you need to purchase the 70-200mm f/2.8L IS II. This means you should invest in at least one good zoom and one good prime initially. I still wouldn't avoid the kit lenses, they're good for how cheap they are, and they are incredibly light weight. You'll still turn out many usable images, and have a range that the zoom and prime you select may not cover. Your wife will even be able to use them without much hassle about the weight. Again, test this at your camera store before investing.
Flash and accessories - Get a separate flash period. It made a massive difference for me in everything I did. The 430 EX II is fine. Tripod is an absolute must, invest well in this item. Don't forget to invest in some filters and hoods.
Total Price: $500 on a P&S, $800 on a Rebel w/kit lenses, I would drop an additional $1200-$1600 in glass, so Neuro's suggestions may be a way to go, $800 on a video camera, and $600 on accessories, or thereabouts.