Acid tells me the firmware is 1.00c.
Seems to be the most common variation.
However, as far as I can tell from the printouts it produces, it does not find/download anything. It makes 4 different attempts, but in each the result is just "no build found for Canon IXUS 130 100c". Seems like it can't find any builds, or am I incorrect..? Is there some other place (on the web) the beta versions can be found..?
That's because the camera is not released. Hence the need to do some testing

I'm also a bit worried about how to format an SD-card the proper way. I do not own a card reader. Is a card reader a must? I do own several SD-cards of different sizes, speeds etc (the 130 IS is not my first IXUS) and if there is a way to use a particular kind of card and just have the camera format it, that would be great.
You'll need a special test build with a ps.fi2 file included for "firmware update" method booting then. I'll see what I can find. I'll also need a real email address to send the link to - I don't post testing version directly in this forum until they are ready. Send me a PM (personal message) with the little "comment" Personal Message icon to the right of this post.
Added: I just remembered that I do have two card readers but they are both really old and I know they do not work with all kinds of SD cards. I was under the impression that most operations needed could be handled via USB (connecting the camera to my mac with USB and manipulate the card while in the camera), but having browsed these pages a bit more I realize that this might be wrong(?)
Unfortunately, you can't format your card for CHDK that way.
If I need a card reader to perform the tests, and use CHDK, I'll buy one. No problems.
In the long run, that might be best. You'll need it for loading things like script files to the camera anyway. There are options using USB over chdkptp.exe but they are still pretty experimental.
Are there any restrictions on what kind of SD card one can use with CHDK? Will SDHC work? SD Extreme? Ultra?
Most anything will work - some older cameras don't accept SDHC but the SD1300 is fine. If you have a1G,2G or 4G card laying around then you are ready to go. Faster cards will save RAW/DNG files more quickly and allow higher quality settings in video modes. Other than that it really doesn't matter.