I'd have to say that the pop-out gauges are one of the really smart things designed into 911s (for the not-so-smart things, see the thread titled 'The Greatest Engineers in the World'). It makes it easy to change bulbs and/or service and swap out the units.
Now, why they made it so that you need a special tool (or a willingness to do damage to the rim) to get the glass out is another issue...
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Jack Olsen
1973 911 T (3.6) sunroof coupe