I have not used elementaryOS so I have no opinion about it, but if its raison d'etre or main differentiator is 'looks' I can imagine why many devs wont be going gaga over it. I care, but I care less about looks than I care about default installed dev tooling, or how well organized its package bundles are. (I believe its packages and package management is pretty similar or exactly the same as Ubuntu). I am less impressed with fancy, memory hogging, terminals with transparency and what not, give me rxvt (not bloated like xterm, but has enough of the functionality) and tmux (well screen will do fine too) I am happy.
For example I like Debian testing more than Ubuntu as I find Debian's package groups better. I couldn't care less about unity. Or atleast I care less than I care about the ease of fiddling with non-mainstream languages. I can trust a whole lot of them being available in Debian testing in the right groups. It might just be familiarity.
Its main differentiator is "user experience" not "looks". This DE is great to use. Of course screenshots only show that it looks good. You need to experience it to really understand where it shines.
For example I like Debian testing more than Ubuntu as I find Debian's package groups better. I couldn't care less about unity. Or atleast I care less than I care about the ease of fiddling with non-mainstream languages. I can trust a whole lot of them being available in Debian testing in the right groups. It might just be familiarity.