How to manage primary key value while multiple secondary server sync with primary server?
There are 3 possible solutions that I can think of to what you are asking.


First solution is exactly how you have it, set each server to increment an identity column by the same increment but start them offset by one. (Server 1: start at 1 increment by 2, Server 2: start at 2 increment by 2) This solution works well because it keeps your key small but allows you to generate them without running into conflicts. On the other hand you have to configure each identity column on each server so you have the maintenance overhead.
Another solution is to set your key to a guid, at 16 bytes the chances of running into a conflict are small, but it's a rather wide key and comes with it's own set of troubles.  See here for more info:  Kimberly Tripp GUIDs as Primary Key  Or here:  GUID vs INT Debate
Use a composite key where one column represents the server that created the record and the other column is an identity that increments by 1. This also has a disadvantage of having to configure the column on each server to represent the server it was created on.


In the end there is no right or wrong way to do it, it's all a matter of what trade offs you want to put up with.