Have been on a merry-go-round of open-source CMSs for a while now. I seem to spend a couple of days once a month, desperately looking for something that fits my workflow. I have to say that this workflow has been very heavily influenced by ExpressionEngine.
Custom fields is the biggest must for me, I am constantly debating with my brother who is an avid Joomla man, the merits of custom fields per channel(ahem 'page') and I can never believe that it just isn't possible in most other CMSs.
I have to say that I've come to PW primarily because I cannot always afford to go the EE route, I genuinely love that platform. I am more and more getting the feeling though that even though I was attracted to PW as a cheaper alternative to EE, it may actually be STRONGER in many ways, though I'm at a very early stage with it.
One final point, Ryan (and others') kindness, openness and support shine through in not only these forums but also the docs and intro videos. If I stick at PW and make it work for me, this will have been a huge factor - I genuinely feel that you care and that is incredibly important.
I got turned off PyroCMS (as one example) because it felt exactly the opposite.