I must say the Pantheon DE doesn't need much changing just a bit on the fonts and .Xdefault colours and a custom BASH prompt, but thats what we do with Elementary OS.. I really like this shell for gnome 3.
My advice is that if Elementary OS have their own snapshot I say that would be your best bet to get the full experience to what the Pantheon DE is all about. Sure you can instal Pantheon DE on Ubuntu 14.04, but I wouldn't do that, and it is more bloated with all that junk that Ubuntu Distro provides.
I use EOS for another reason, no amizon ads and all that Internet Suggestion malware crap that Ubuntu injects in their distro, and to EOS it's simple clean and none of that bullshit. Luna is based off Ubuntu 12.04. I really can't wait until it is ported to Debian. I tried to get Patheon DE to work on on Arch Linux but meh whatever didn't work all that great, not like Elementary OS lulz (of course right duh). Gentoo has it ported as well, but meh.. when debian have it ported it should be just as good as Ubuntu since Ubuntu is based on Debian .
Also to me I don't care if i use Ubuntu 12.04 or 14.04 as long as I have the programs I use everyday and it supports all my devices i'm ok with it. Umm Elementary OS said once 14.04 Ubuntu is out. Elementary OS v0.3 isis should be out not long after, which will be based on 14.04 Ubuntu. So if you want to wait, isis will be based on ubuntu 14.04, if you don't you can use Luna which is Ubuntu 12.04 and its not bad at all man I love it. It is a better Ubuntu and also a better shell for gnome 3 = NICE!
It's entirely up to you. You can upgrade 12.04 to 14.04 and luna to isis once it is out. They say its better to do a fresh install, but they alway say that with "Ubuntu" base i have upgrade alot of Ubuntu base with no problems. It's just sometime it can have flaws so that is why they say that. Also it's good to know what your doing.
I've been Using GNU/Linux for 14+ years and Sun OS , and BSD for along time so UNIX is not really new to me.. (I still don't consider GNU/Linux like unix at all, I do however consider to be more like Windows NT type system). GNU/Linux is doing really good to fully replace Windows NT right now. Everything I needed for windows in the pass now I can all do on Elementary OS. So yeah it is worth a try man.. you can run a LiveCD without installing it befor hand, if you are just wondering about the OS.
THe little programs that come with it is ok i dont like noise, i rather use clementine, but thats me... calender , and the tweak tools are GREAT GEARY Email Client I really love this app very cool client. umm whatever plank is a nice dock i use it on my freebsd with openbox i also use it with DragonflyBSD 3.7.1.
Yeah... one problem with the global menu is that I had some bugs with it man.. i just use the the icon as a menu instead of having text "applications" i just have a icon for the menu and i took out global menus because it would not align good after awhile with apps and like wehre it says file edit etc or whatever it is be like not align with the icon on the left it be more like a gap between it like the icon and the clock and it just was kind of buggy and flakey for my liking..
but hey it make work better for you.. everybody computer is different right.. i dont care i dont need global menus... though having a icon for the menu is better than text i like that feature also changing the fonts on the shell and terminal and all that is a nice feature as well and works perfect with the tweak tooks.