I didn't have any issues installing the Softube Acoustic Feedback Deluxe plug-in as it was just about as easy as installing any other plug-in out there. It was just as easy to figure out the interface of the software as everything is easy to understand. The plug-in has parameters mix, feedback, and tolerance. This is all there is to the plug-in so as you can see it shouldn't take users too long to figure out everything that is going on. Since it is so easy to use, a manual isn't necessary.
I am currently running the Softube Acoustic Feedback Deluxe plug-in on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM and I run the plug-in in Pro Tools LE 7.4 that runs with a Digi 002R audio interface. Within this configuration I have been able to run this plug-in without any problems at all. I don't tend to run too many of them in a single session so I don't know how many you would be able to run at a time, but this probably isn't a plug-in that you would want to run too many of them anyway.
I've been using the Softube Acoustic Feedback Deluxe for six months or so and I've found it to be a pretty cool plug-in. It isn't something that I use on a consistent basis, but I do like having it around when I need some realistic feedback if I don't have any recorded material to use. You can get all sorts of feedback sounds with this plug-in and it is great for experimenting with. The price of the plug-in isn't much at all so if you are looking for a cool feedback plug-in, definitely try this plug-in out as I believe they have a good demo available on Softube's website.