Well, along the lines of what is already mentioned, I stumbled on web communication aspects (I like the available template system, it performs well) and ran into glitches with the mongo or postgresql drivers as I got deeper. I am glad that Nim doesn't have a Ruby-like syntax -- Nim's current type structure/syntax is its strength, IMHO.
(I wanted to contribute some money to the team but PayPal is the only option even if the site says it can take Visa etc. PayPal is something that I avoid due to past experiences)