The main difference (In mapping) is that you need to convert your maps in doom3 or quake4 file format (map file format!).
And, that xreal doesn't use q3arena style shaders, but instead id4 tech materials (very similar to shaders, but a bit different).
If you are using GtkRadiant 1.4 transforming the map is piece of cake (unfortunately, if you use 1.5 like me, then you have to realign all the textures or fu*k with gtkradiant 1.4) Take note, that first process is optional, it is necessary only for preserving the original texture alignment and scale - eg. you don't need it if you want to convert only the bare brushwork.
The transformation process:
1.) Load gtkradiant 1.4 (it is important, that all of the textures used on the map are loaded! - eg. no shader image missing warnings!)
2.) GoTo: File>Project Settings>Misc Settings - Use brush primitives in MAP files (check box has to be checked )
3.) Click OK, then Reload the radiant(1.4)
4.) Backup your original MAP file!!!! - just in case!
5.) load your MAP file (only if you have a backup copy!) into radiant(1.4! not 1.5!)
6.) Radiant will ask you if you want to convert the map, choose Convert
7.) save the map.
Then convert your "transformed" map into doom3 file format:
Using Q3toD3
http://www.quake.de/q3tod3/ (set "path to doom3" to xreals path and q3 path to ET path)
Or using Xmap.exe that is provided with xreal.
Converting with xmap.exe:
1.) Copy the transformed file into /xreal/base/maps/
2.) Open console (or command in Win)
3.) run "xmap.exe -map2map -quake3 pathtoyourmap.map
(you have to specify the full path to map eg. c:\Files\xreal\base\maps\mymap.map, otherwise it won't work)