I wrote how to do a basic Arch Linux installation on the Thinkpad T450s in this article. I will now describe what to install and configure next to be able to really use it. The desktop environment I'm using is GNOME so some instructions will be specific for it.
The new elementaryOS Freya has been released some months ago, but I'm writing this article now to be able to give you a feedback after a long usage. I've been using this distribution since 0.2 Luna and I'm going to give my opinion of the new 0.3 Freya.