>Well. GUIDs would help during company mergers. The NewSequentialID() function in SQL Server produces a GUID that is serialized to fill the index data pages, making inserts very fast, and more efficient that regular GUIDs. It takes up more space, than an int, but potentially far less than primary key on several data columns. :)
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That's sort of how I feel.

My own two cents is that true GUIDs are going to be beneficial for (as you said) company mergers, and loads from disparate systems.

As for the NewSequentialID, in SQL 2012 there's almost no need for it. The new sequence object is like a table-independent identity value, and can be used for an int or even a bigint. I agree that NewSequentialID is better than a regular GUID, if uniqueness is only necessary in the database.

What has bugged me over the years is seeing people abuse GUIDs - using them when it was completely unnecessary. I've run into clients who weren't aware of the fragmentation issues. Not an indictment of the feature itself, but of the database people who didn't know any better.