My wife has the Canon
SD-870. A great little compact. (Also has the time lapse feature!) I have shot with it and it is a great little camera. Nice and small and fast without all the extra controls like on the G series that she will never, ever use. I also had an older Sony and was quite pleased with it. (you may check out the SD-880 or SD-890 for newer models).
As far as adapter lenses, yes, the
G9 and
G10 both support them: The G9 has either a telephoto or a wide angle attachment and the G10 has a telephoto attachment only, all sold separately. HOWEVER, the wide angle attachment for the G9 is
frickin' HUGE! I bought it for mine and had no idea how big it really was. It weighs more than the camera and I only ended up using it twice because it defeated the purpose of carrying around a smaller camera.
The Panasonics are good, but I had one (
DMC-LX2) and the digital noise was horrible even at 100iso. It is a shame too. They put a nice sharp Leica lens on a camera with a crappy sensor. What a waste. The TZ4-TZ5 are supposed to be great compacts but the reviews I have read said their one fatal flaw is the poor sensor. I do like the Panasonics, though, and wouldn't turn one away. They are worth looking at.
Again, the G series are great cameras IF you are looking for a lot of manual controls. If you are going to spend most of your time shooting candid shots on automatic mode, it may be more than you need. In fact, it will be. Spend less on a less featured camera and you will be happier for sure. If I had given my wife a G series instead of the camera I did, I am sure she would not use it enough.
I am not to familiar with the Pro 1 nor it's interface. The main difference I see from the G series is that the lens doesn't collapse into the Pro's body making it a non-compact. The G series do fit in my pocket. Also the Pro has a flip screen which the G series discontinued. It looks like the controls are quite different as well.
By the way, I did just get the G10 on Friday. B & H was selling them at $414 with free overnight shipping. Couldn't resist (and the wife said go for it.) Despite the loss of the time lapse feature, I really like it. (I'll bogart my wife's camera for that! Mwuhahahah!) It is slightly larger than the G9 but not enough to make a difference. The start up time is much faster than the G9 and the wider angle lens is really what I was after. I am almost sad to give E-Bay the G9 though but I can't keep two.