I recently got the SD780, but I can still take it back (Costco's great that way), so I'm wrestling with this same dilemma. I'm attracted to the shorter-and-longer-and-faster lens of the SD940.
Using CHDK on the SD780 is great. RAW makes this camera a significantly better shooter. (The in camera's own noise reduction is definitely smeary, and the combination of sharpening and jpegging produces some ugly artifacts. The RAW files are often amazingly good, however.) Enabling Superfine mode is a terrific advantage for snapshots, or if you need to conserve card space and can't shoot RAW. The lens could be a little sharper, (it'd be nice if they put an aperture in these cameras) but even CHDK cannot help that.
Zebra mode crashes the SD780, (a known fault) but it's the only CHDK feature I've tried which has not worked. The CHDK improvements in this tiny package make a terrific shooter. I probably wouldn't buy it without the CHDK advantage, however. I'm not wild about what it puts out in its native state.
I would assume all these improvement would apply to the SD940 when it's ported. (I wish I could do the port, but I know my limitations.) I'm not sure if the deficiencies of the SD780 in its native state might also apply to the SD940; I'm hesitant to prejudge, and I have not had the opportunity to shoot with one.
Is someone porting the SD940 yet?
Thanks.
