主键 - 本机键，序列键还是GUID键？

In reading this and this and then reading this (which references the other two ironically) I find myself wondering just how big the discussion of this topic is? I am a SQL Server guy and so I tend to use an Identity that is auto generated in the form of an int. However, when I know that I will need some form of replication between server and server or synchronization between client and server I tend to use a GUID as my key.