Just thought I would test the water around the community and see what consensus was on synced aps and if they needed the gps moduals or not and if there was benefit or somehow detrimental.
It really depends on what your needs are. If you're deploying in an area where there's plenty of unused spectrum and/or maybe it's a smaller site then you'll probably be fine just using the non-sync'd radios. If you're looking into deploying at a site with limited spectrum available and/or interference, you'll be better off using 1000 GPS, or the 2000 (which comes with GPS sync).
The sync products help you eliminate self interference, and also allow for back to back frequency reuse, which can be valuable if you're dealing with a limited amount of spectrum.
You can also swap out a non-GPS unit for a GPS unit later down the road if you need it... and there are 5GHz 'lite' 1000 GPS radios (10 sub limit, and then if you want more you have to buy an unlock key) available for less cost then the full blown 1000 GPS.
You typically only need to buy a GPS unit for the AP, or for the master side of a PtP link, you do not have to buy GPS units for the clients or slave side.
One last thing, the 1000 GPS units support gig-e, whereas the plain connectorized ones only support 100mbps eth. So in a point to point situation, if you're using 40MHz channel widths, and the RF is capable of more then 100mbps, you might want to consider getting the GPS capable units on both sides just so you're not limited by the 100mbps ethernet port on the slave side.