that was sort of a planned change, but it has regressions - most notably, makes map editing much harder as identifying map elements now is impossible without opening their properties individually. same goes for all other macros, as before it was possible to simply add a macro to reference item value and immediately see whether it was correct - not possible anymore.
possible solution would be a "resolve macros" mode - by default they would not be resolved (improves performance), but could be easily enabled.
this functionality was lost during development of ZBXNEXT-674
That's the difference between Monitoring and Configuration sections. In Configuration we tend to display configuration parameters as they are without substitution of macros. That's the general approach we applied to maps as well.
I agree that a special "Preview" button would be a nice touch though.
after some discussion this was decided to be a serious enough regression in the editing mode to warrant a blocker priority 
rough initial specification at https://zabbix.org/wiki/Docs/specs/ZBX-4009
<pavels> I think it should affect everything in the map configuration, not just the map itself. Should we resolve all of the macros, or just some of them, e.g HOST.NAME or IPADDRESS? Someone also had a nice idea, that the resolved macros should be highlighted with some color to separate them from plain text.
dev branch: svn://svn.zabbix.com/branches/dev/ZBX-4009
Successfully tested!
MERGED: svn://svn.zabbix.com/trunk 24241
Just for case - do not forget to update http://www.zabbix.com/documentation/2.0/manual/introduction/whatsnew200 with this feature.
Added note to What's new.