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.
This is the AIR Chorus on steroids. There are all kinds of crazy options in here to get whatever chorus modulation you're looking for. In fact, it's like combining multiple AIR Choruses together and having them in one convenient plugin. It might be a bit more daunting than the regular AIR Chorus, but the added benefits are definitely worth it if you're looking to create your own unique chorus.
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 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've only been using Pro Tools for a few months, so my opinions may change in the future.
The AIR Multichorus is the plugin that I probably use the most when I want to create a chorus effect inside of Pro Tools. It's more versatile than the regular AIR Chorus, and it sounds amazing. Just be careful not to overuse this as it can get ridiculously 80s sounding if you're not careful.
The Digidesign AIR (Advanced Instrument Research) Multi-Chorus is a plug-in that comes free with the newest version of Pro Tools. Users of Pro Tools 8 will get this plug-in for free when they upgrade or buy an audio interface with the Pro Tools software. It installs during the initial installation process of Pro Tools 8, so no further action is needed to install the plug-in. The interface of the plug-in makes it a pretty versatile one as it includes setting controls for rate, depth, low cut, width, pre delay, waveform, the number of voices, and mix. It has a very similar interface and make up as the AIR Chorus plug-in that also comes free with Pro Tools 8, but allows for a thicker sound with more perceived voices. I don't think that a manual is something that is necessary, if one exists at all.
Having just upgraded to Pro Tools 8, I'm now running the Digidesign AIR Multi-Chorus on my Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run Pro Tools 8 with a Digi 002R interface or a Digi 002R audio interface depending on if I'm on the go or not. To date I haven't had any issues at all running the plug-in within this configuration, as the plug-in definitely doesn't take up much processing power at all. I only first used the plug-in a few months ago when I upgraded to Pro Tools 8.
For Pro Tools 8 users, the Digidesign AIR Multi-Chorus is a great tool to have, especially at the price it is at, which is free! I like this plug-in a lot as I think the tone quality is clean and that you can do a great deal with it. It is possible to get a thick chorus sound from this plug-in without a doubt, whether it be on vocals, electric guitars, or whatever else. Both this and the regular AIR Chorus can do some pretty cool things, and both are pretty unique to each other although they do share some similar overlapping tones as well. Everyone who has Pro Tools 8 should absolutely have at least checked this one out by now, as it is a very useful tool.