I think that I'm not the right person to speak about Chevereto as a customer and of course that for me Chevereto is pretty good. However, I will try to be the most honest that I can in this post . (if you didn't notice I'm the author or Chevereto):
1: How good is the script overall?
Overall (to this present date) is good enough and it does what it says that it does. The most important issue is that Chevereto (current release) has a limited set of features. While the other folks already have user system, affiliates, etc. we only have what is listed here:
http://chevereto.com/download This is because Chevereto is a very old project and every step is heavily tested, we are breaking ice here. Before Chevereto 2.X the image hosting script was a pale desert area and since Chevereto appeared a lot of scripts has come (and a lot of them have died). Now we are at the gates of the 3rd major release and you can find the feature set here:
http://chevereto.com/community/threads/chevereto-3-feature-set-final.3288/ (That is like 30X the current V2 release). That is how I deal with the leak of features, developing an amazing thing instead of just do crappy implementations.
2: How stable is the script?
Well, define stable. If you meat that the script will screw your machines or burn your CPU, well.. I have no record of the script doing that (or any script whatsoever) because that issues are most likely on the server rather than the script. If you meant stable in the way that the script is well supported.. Well, take a peek here:
http://chevereto.com/community/forums/tech-support.16/
Now, V3 is the biggest thing since Chevereto V2 and it will set a lof of new things like that Chevereto will run two frameworks (Front and Backend) just because the development in V3 is so intensive that I need to order things. And these frameworks are custom made, they have been developed from scratch for Chevereto. Do you know anyone else doing that? Nope... And that is because I realize that scripting business has a lot of downsides and a lot of folks like you have been heavily dissapointed with them. You should read my last blog entry because is about what happened with you and those scripts.
http://rodolfoberrios.com/post/59656144217/the-decadence-of-scripting
Chevereto has more than 1000 clients and a lot of installations out there. That is the best benchmark that you can get. Of course that Chevereto is not perfect and the current version every day feels more old but with V3 things will go up again. Finally, if you want to know more fell free to read the Wikipedia
http://en.wikipedia.org/wiki/Chevereto or ask clients/users around here. If you browse the forum you will notice that I'm very close to the customers and I actually take care of hear them.
Cheers,