Hey DataGhost, your build 51 is working pretty well on my S5IS. I have encountered a couple of interesting issues, though:
As you noted above, [Shoot] to run a script freezes the camera, and then it crashes. (Haven't tried toggling the flash up and down yet.)
Uhh, I thought I fixed that. Did you immediately download it after I initially released it? Does it still crash with the current download and if yes, what exact settings/script did you use?
There's a white rectangle poking up into the bottom of my screen during record mode. It stretches from the left edge to the middle, but it's only a few pixels high, maybe 10. Any idea what it is?
If you don't know the purpose of some OSD element, go into the OSD layout editor and navigate to it with the SET-button. You'll then see it's name.
I can't start in record mode, even if I flip the [On] lever that direction to turn on the camera. It always starts in Playback mode instead. Repeating the [On-Record] push gets me into Record mode, though.
Yes you can, hold the lever until you feel/hear the lens extend. It's probably something I can fix, though, I didn't really care about it anymore. I started my camera about a thousand times with that hold-until-done method so it became a habit

I did experience at least one other crash, can't remember where. Is there any way for me to capture debugging info, or is it too late by the time the crash happens? :-P
Well, I don't really know a lot in 'final' CHDK that can aid in debugging (in normal shooting modes), so you'll just have to supply me with as much information as you can to reproduce it.. what settings were you using, what key(s) did you press, in what order, etc.
@jaydee: You'll still want another camera if you're thinking about concert photography or other low-light conditions where flash is not allowed, because the S5 noise over ISO200 isn't really acceptable anymore. I did manage to take some decent pictures at 1/13 F2.7 ISO200, but for that purpose I'd much rather have an EOS which can do ISO3200 with about as much noise as the S5 on ISO400. The S5 is quite a good camera for everything else, though

Especially in value for money, I effectively have a 648mm IS lens, something like that for an EOS would cost several times the S5 and then you still need a camera body.
I didn't really port anything besides 'basic CHDK functionality'. I'm currently looking into other S5 addons/features, but they require a good deal of RE, thinking and time.