Anecdotally, ArchLinux has bitten me before with its rolling releases. They moved the hostname utility to a new package, but pacman (their package manager) didn't prompt or download the new package. This promptly broke my laptop's network stack right before I left for a weekend trip. Now I didn't have internet, and I didn't have internet to find out how to fix my internet. It all worked out fine by writing a bash script named hostname sitting on my path that echoed a constant string, so I could connect and download the new package.
If you are looking for a pain-free linux system, Arch Linux isn't it. You will run into little things like this, living one step behind the bleeding edge (basically someone compiles your software for you, does a sanity check, then you get it ASAP). Don't get me wrong, I love it, and will continue to use it as long as it has the most flexible and clean system, because I appreciate their dedication to simplicity of implementation.
I ran Debian unstable on my desktop for a number of years and the experience sounds pretty comparable. For the most part I just got working bleeding edge packages with minor quality control. Occasionally you would get some breakage (which was usually mentioned in apt-listbugs before upgrade anyway), and the nice thing about debian was I could either pin the package to the current more stable version, or if I had already upgraded I could just grab the previous package off of the debian snapshot mirrors.
I would argue that yes, debian unstable and arch are both rolling release distros, so the experience will be sort of similar, but I think that's where the similarities end.
Arch on one hand has a large user base (everyone) using the rolling release packages, this means that bugs get quickly found and squashed. There is also a testing repository which is used for the "base packages" so major bugs don't get get past into the "stable" repos. For example, kernel 3.1 is still in testing because of some problems that the testers experienced.
On the other hand, debian unstable has bitten me more than once very hard. So from my experience, it feels like debian does very little if any Q&A on debian unstable. I would compare Arch to Debian testing more since by then, packages have had some time to test and mature.
That said, I've experienced less crashs on arch than on any distro. Mind you I actually read the news. I honestly can't even remember the last time I've had a crash on archlinux.. maybe several years ago with some kernel update.
I wouldn't call making /usr/bin/python point to python3 stable. I got nothing against their philosophy per se, but let's not make it something that isn't. a primary feature of a 'stable' system is that you wake up to the same one you left the day before.
If you are looking for a pain-free linux system, Arch Linux isn't it. You will run into little things like this, living one step behind the bleeding edge (basically someone compiles your software for you, does a sanity check, then you get it ASAP). Don't get me wrong, I love it, and will continue to use it as long as it has the most flexible and clean system, because I appreciate their dedication to simplicity of implementation.