Paul,
The US Army ADA has adopted the Bradley fighting vehicle as a SPAA vehicle; 4 vehicles to a platoon and each vehicle has a Stinger dismpunt team as well.
The M6 Bradley Linebacker which replaced the TOW launcher with a 4-Stinger pack were converted back to M2 IFV configuration in 2006. The gun was just the existing M2's 25mm chain gun, which like all the IFV's (BMP-2, M2, CV-90) cannon can be quite useful against helicopters, but little use against anything faster.
Justicar kindly alerted me to the LAV-AD which had 2 4-Stinger packs and a GAU-12 25mm gatling type cannon. The GAU-12 was a much more potent AA weapon than the M6's 25mm. Also apparently no longer in service.
While both had good comms and the ability to be pointed to targets by the local air defense radar network and were equipped with white and IR TV systems, neither had their own radar systems, a failing that they shared with the much older Soviet BRDM SA-9 variant.
I was particularly interested in AA gun systems. While missiles have better ranges and TK percentages, they can be spoofed to varying degrees, gun systems are shorter ranged, less accurate but still can be aimed by various optical means and do have dual use. Missiles are more expensive and in more limited supply than 23, 25, 30 or 35mm ammunition. A mixture of guns, radar and IR missiles makes the opposing air forces task much more risky and complex. While the German Gepards have gone/are going out of service, the Poles and South Koreans have their own equivalents with 35 mm cannon. The Soviet Shilka has its Tunguska replacement (2 x 30mm guns & missiles) and the Chinese have their PGZ95 (4 x 25mm guns & missiles). All with on board radar.
Having an onboard radar system means that if your local air defense network gets taken down by ARMs or plain old artillery or iron bomb air strike, then each vehicle can still search as well as track on its own. Of course a radar system can IFF whilst an IR based system can't, so is not as safe to friendlies, which may inhibit or degrade your AD response.
Just like a mixture of tank guns, AT missiles and artillery make a land attacker's task more difficult by covering each individual system's limitations, AA guns and missiles mixes also cover each other's backs and act as force multipliers. Even if the number of shoot downs is low, minor damage can prevent prompt repeat air attacks and eat into spares.
Virtual attrition is also a problem if more attention has to be given to eliminating a multitude of small mobile AA platforms as well as causing mission aborts and misses. It can be a problem also if you run out of expensive ARMs when your enemy still has some Shilkas or Gepards left.
The main reason I mentioned the failure of the M247 is that I was a bit perplexed that US, with its great technological lead, never developed a good SP AAA system during the cold war while the Germans, French and Soviets did. I do not regard the M42, M163 or ZSU-57-2 as anything other than fairly marginal except against helicopters.