I tend to be a fan of Ubuntu LTS, Debian, and Cent OS vs. Fedora, Ubuntu Non-LTS, Arch, and other distros that while very cool for testing and bleeding-edge, severly lack in stability.
Both Zorin OS 4 and 5 are based on the Non-LTS versions of Ubuntu, which are really betas for the next LTS (12.04). Since Ubuntu's LTS starts out bieng pulled from debian-testing and the Non-LTS versions are pulled from debian-unstable, so therefore it's true that any distros forked from Ubuntu ( which Ubuntu itself is a fork from Debian ) will also come from these two sources of debian-testing and debian-stable as well. Linux Mint and Zorin OS are both forks of Ubuntu and are both affected by this.
I'm all for testing, bleeding-edge, etc,..... just not on any production / critical / main systems which I use. So that all being said, I like Zorin 5 for what it is, but because of the lineage back to debian-unstable, it (much like Zorin 4), doesn't work for me very well (and in some places, not at all.)
If I have a suggestion, it's more for Zorin in general than for a specific version; and it's this:
I recommend promoting the latest and greatest versions, BUT making it clear that Zorin OS 4, 5, 6, 7, etc, whatever version(s) that may be, aren't as stable as Zorin OS 3.1 is (since it's based on Ubuntu 10.04LTS). As such, please put a note comparing 3.1 and 5, with clear links to both on the Zorin OS homepage for downloding them. For the average Linux neophyte, Zorin OS 3.1 is my main choice to recommend - and it is the version I install on newly refurbished systems which I donate to people who need computers.
Lastly, I have downloaded Zorin OS 3.1 Ultimate and would like the passwords for both the 32-bit and 64-bit versions of it; but I don't see anywhere to purchase them - only the orin 5 Ultimate versions. I'd also like to know exactly what the differences are between the Free and the Ultimate versions of Zorin OS. I know one difference is the Mac GUI, which isn't a selling point for me at all.
For those who want to customize Zorin, I write a script to modify Ubuntu (thus it works with Zorin OS, Linux Mint, Ubuntu, etc) http://sourceforge.net/projects/ubuntune/
which can be downloaded and read in gedit. It's highly commented inside of the script so that you can see and understand exactly what's going on, where, when, and why.