An interesting article, but there seems to be one aspect that has not been covered.
The article suggests that there is a slight overhead using a surrogate key (as an extra column is created ), however actually this can lead to a massive saving where foreign keys are concerned.
if your primary key is nvarchar(25) (50 bytes ish) then your foreign key in another table is also nvarchar(50) - this child table may have many times more data than your parent table, so using a surrogate key of INT will drop your storage and retreival costs significantly. (down to 4 Bytes)
so in a scenario where we only consider 1 table with 100,000 rows then yes we have an extra 400,000 bytes data, but in a scenario with 2 tables we actually save 4,600,000 bytes
ok my maths might be slightly off, and yes it's VAR so we don't always store the entire 50 bytes of data, so my saving is slightly exagerated, but it does demonstrate the point that a key should be as small as possible...
I'd love to see the article expanded to test the same scenario but using a join