Ubuntu touch is still in development. Not 100% stable, a bit slow, and not complete for 100 % of users.
But for developers it’s a perfect OS. Full GNU/Linux based with a true terminal and the os is 90~95 % open source (core app, mir, unity, etc … are open source, but some driver are still closed source, not sure). (so no virus on Ubuntu Touch :D)
Also convergence make Ubuntu touch unique (in the future Linux applications will be able to run on Ubuntu touch).
The bootloader is open. I had read on ask.ubuntu.com that ubuntu touch needs a unlocked bootloader, that why the bootloader is unlocked on the MX4 Ubuntu edition
It’s also because canonical react quickly.
There was a malicious app exploiting a system vulnerability in Ubuntu touch, the day after a patch has been released : http://news.softpedia.com/news/first-malicious-app-published-in-store-for-ubuntu-touch-494595.shtml
About the bootloader I can’t find the message where I read it :(
Just got email from meizu that ubuntu edition PRO5 is for sale :
Thanks again for signing up to be kept up-to-date on the availability of the Meizu PRO 5 Ubuntu Edition.
You can now order the Meizu PRO 5 Ubuntu Edition here ( http://en.jd.com/1104324.html )or here ( http://www.jd.ru/1104324.html ), after which it will be shipped to your house within a matter of days.
For more information, please check the Meizu PRO 5 Ubuntu Edition product page or get in touch with us via email@example.com.
Your friends at Meizu