Since I started working as an Assistant Librarian I have learnt to use RefWorks, because that's what most of our academics use - and it's really useful for me to know how it integrates with the repository. I like RefWorks, and find it easy and intutive to use. But I've been keen to experiment with Mendeley for a while, because it also seems to be quite well-used amongst our academics- and is often mentioned in relation to repositories.
After reading the info about Thing 14, I was also keen to experiment with Zotero as it sounded like the best of the three referencing tools mentioned. After having a bit of a play, I really liked how easy it was to import references into Zotero, and the way it just automatically attaches full text where a PDF is available is great. (I should probably mention at this point that I use a Firefox browser at home, through choice, so the fact that I couldn't use Zotero in IE didn't really bother me). However, I found exporting the references out of Zotero somewhat less intutive. It was fine once I had figured out exactly what buttons to click, but it took a bit of a play to find them. The Start guide was of some help, but it didn't feel like I was being told everything I needed to know. This is only my first play with Zotero, but it's something I think I'll use a lot more in future (both for keeping track of my own references and suggesting to others) on this evidence.