I just upgraded from the S3 to the SX10 earlier this month. I don't think it's hard to use - it has many of the same functions, just in diff. places. I don't know if you saw my post earlier on this thread:
S3 vs SX10.
Last night I used my SX10 to take some photos during rehearsal of our high school musical. I haven't even had the camera for a month, but I was able to change settings in the dark auditorium, so I'd take that to mean that it really ISN'T harder to use than the S3.

I was experimenting with center-weighted vs spot metering, sports mode vs program w/ISO 800, single-shot vs continuous shooting, stuff like that. I haven't had a chance yet to download the photos to my computer to see how they came out.
One function of the SX10 that I don't think I'll use is the High ISO 3200 setting (under the Scene mode on the dial). I tried it just for kicks for one photo last night, and the noise was horrible just looking at it on the LCD. I can only imagine how bad the noise will be when I see the photo on my computer screen!

I don't know when anybody would use ISO 3200 anyway, unless there's a photo you just HAVE to get and there's no other way?