Recent Experience
For what it's worth, I recently used a loner MacBook Pro for a week while mine was in the shop. Because I mostly use my mac to develop software for unix servers (typically using case-sensitive ext4 file systems) I decided to give HFS+ case-sensitive another try.
For me, all core OS X applications worked perfectly and I didn't notice any stability issues with the system at all. Also, most of my third-party software worked without a hiccup.
But there were exceptions. When I decide to give this a go, I already had in mind a number of programs I expected to break, and a few of them did. Most notably, ALL Adobe software refused to run. Because Creative Cloud requires that it is installed on your boot volume, a case-sensitive boot disk is a show stopper.
Generally, though, there are better-built alternatives to these brittle codebases. For example, I began using Affinity's Designer and Photo instead of Illustrator and Photoshop, which almost perfectly fit my use cases.
There were a few pleasant surprises: Backblaze continued to work and Microsoft's Remote Desktop was still able to be used.
I don't have any other Microsoft programs so I can't comment about Office apps, etc, which might be a bit iffy.
My Plans
Once every few years, I totally rebuild my system from scratch instead of upgrading. I'm planning to do this when El Capitan is officially released, and I will be using a case-sensitive file system. As I see it: any software that is unable to run with case sensitivity is probably not something I want to be running at all. If there is something that I absolutely need, I can always run it inside a case-insensitive VirtualBox VM.
[[ Update 2015-10-15 ]]
I've now been on HFS+ Case Sensitive for over 2 weeks on El Capitan, and I haven't had a single issue. Of course I haven't even bothered to install the software I knew wouldn't work (Adobe), but I haven't run into an issue with any Apple software, App Store apps, or open source code. If you spend a good amount of time developing for unix systems, I'd highly recommend making the leap.
[[ Update 2016-09-23 ]]
Well, it's been about a year now, and I'm never going back. I'd encourage all developers to always use a case sensitive filesystem. Also, it should be noted that the successor to HFS+, APFS, will become the default filesystem for macOS, iOS, and watchOS next Spring, and as of now it's only available as case sensitive.
Best Answer
It's a better practice to leave all uppercase variables for the shell and use lower and or mixed case for user variables in scripts. You need to preface the
hdiutil attach ...
command too withsudo
if using/.000
as the mount point.Here's my version of the script which works.