AIR plugins are part of the set of plugins that come together with Pro Tools. AIR stands for Advanced Instrument Research, and these are highly versatile plugins that really help expand the overall usage of Pro Tools. First of all, there are no compatibility issues with these plugins as they're made exclusively for Pro Tools. That means no unexpected crashing or weird bugs. I never read the manual on this, so I can't really comment on that. These plugins are easy enough to use that you shouldn't really need it.
AIR Chorus is a good, solid chorus that you can include on any buss to help add that thickness and depth to your mix. It can do everything from a subtle modulation to an insane 80s chorus delay that sounds like you're under water.
I never experienced any performance issues with these plugins, and the reason is that they're made exclusively for Pro Tools. Because of that, everything is rock solid. I use a Mac Pro Dual Quad Core machine, and while Logic is my main DAW, Pro Tools is what I've been experimenting with lately, and I can see why it's considered the best DAW out there. I never had any issues when it came to RAM or slowdowns, but it could also be because my machine is fairly hefty. I've only been using Pro Tools for a few months, so my opinions may change in the future.
One thing I dislike about these AIR plugins is that they're only found in Pro Tools. While other DAWs have their own exclusive plugins, I'd like to see these available for purchase at an affordable price. That would help out both DigiDesign and everyone who uses a DAW besides Pro Tools. The plugin itself is nice, and I've used it quite a bit with great success, so no issues there.
The Digidesign AIR Chorus plug-in is one that comes free with Pro Tools 8, the newest version of the software. In my opinion, it is worth upgrading to Pro Tools 8 from a previous version just for the plug-ins, as there are a ton of new ones under the name AIR (Advanced Instrument Research) and otherwise. This of course is in addition to a ton of new features including a new way to comp and an interface that is easier on the eyes in my opinion. You don't need to do anything to install AIR Chorus, as it automatically installs when you install Pro Tools 8. The interface of the plug-in is very straight forward, as is the case with most of the AIR plug-ins. This one has sections for chorus and LFO, the former of which has parameters for feedback and pre delay, and the latter of which has those for waveform (triangle or sine) and L/R phase. It then has parameters for rate, depth, and mix to round things out. I don't believe that they make a manual for this one, but one isn't necessary either way.
I only recently upgraded to Pro Tools 8 on my home studio, but have been using it and the Digidesign AIR Chorus since they first released Pro Tools 8. Right now at home I'm running it on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run Pro Tools LE 8 with a Digi 002R audio interface or a Digidesign Micro Box if I'm on the move. I also had been previously running it on a Pro Tools HD system. In either scenario, I didn't have any problems at all running the plug-in, as it takes up a very low amount of processing power.
For a free plug-in, the Digidesign AIR Chorus is really great to have around. I wouldn't necessarily pay for it, but it has definitely come in handy more than I thought it would. It has a pretty clean sound and is capable of getting a good amount of varying tones, as there are definitely a nice amount of parameters to work with. If you've got Pro Tools 8, get to work and try out these new plug-ins including AIR Chorus, as you'll be glad that you have them and even happier that you got them for free!