I would say keep it, based on two points:-
1. fluctuation check - As PhuketPaul says, with an SPG you get a good fluctuation check when you try breathing before entering the water. Doesn't generally work with AI, or if it does, the time taken for the pressure to drop significantly is too long.
2. other guages - my SPG is part of a triple set. SPG, Depth, and compass. Keep SPG, keep all. If I lose the SPG I would have to add a compass and depth guage somewhere else.
Just remember, with AI only, if you lose the computer, you lose everything, no time or depth, or way of seeing your ascent rate etc.... . Personally I would like some backup.
Diving with a non AI computer, most people I know still use a triple guage and have a watch. This gives them a redundant depth guage and dive time. Going AI, why would you then throw away this redundancy by removing the guages? or with a non AI computer do you not have a depth guage and compass, only a single SPG?
Jon