The McDSP ML4000 Mastering Limiter is a plug-in designed for use for mastering, but is also suitable for other limiting purposes. After downloading the plug-in from Massey's website, which has an almost fully functional demo available for free, I had the plug-in running within a few minutes. The only limitations that the demo has are that it will reset its parameters to default every time you re-open it and you can't save any of your settings. You also can't bypass it, but the plug-in is cheap enough that it won't cost much to get the full version.
Since the McDSP ML4000 Mastering Limiter is indeed a mastering plug-in, I generally only use one of them on the mastering fader. However, it doesn't take up too much processing power and if you wanted to use this for mixing I don't see why you wouldn't be able to run a few of them at once. I am currently running the plug-in on a Mac Book Pro that has a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM. I run the plug-in in Pro Tools LE 7.4, but have also ran the plug-in on a few different Pro Tools HD systems and it works great on all of them.
I really can't say a bad thing about the McDSP ML4000 Mastering Limiter. I've been using it for a few years and really like everything about it - the sound quality, the ease of use, and of course the great price. Even though the demo is great to have, to buy the plug-in doesn't cost much at all and it is nice to be able to save settings and bypass it. For this price this is definitely the best mastering limiter plug-in that you can buy, and to me is one of the best deals out there. Definitely go check out this plug-in and all of the plug-ins that McDSP has to offer as they sound incredible and are incredibly cheap!
The McDSP ML4000 was quick and easy to install without any problems. I had no compatibility issues and since I bought it electronically, it was transferred straight to my iLok and had the plug-in running in a matter of minutes. I bought this plug-in with the Project Studio LE bundle and have had no problems with any of the plug-ins in this bundle since I installed it. I don't have a manual for this, but it is easy enough to use that you shouldn't need one.
I am running the McDSP ML4000 limiter plug-in in Pro Tools LE 7.4. I am running Pro Tools on a Mac Book Pro with a 2.2 Ghz Intel Core 2 Duo processor and 4 GB of RAM and a Digi 002R audio interface. I am able to run a few of these at once if I choose to, and it has always run smoothly and stable with this configuration. While you can run a few of these at once, it is more of a mastering plug-in and is meant to be used on the master fader.
I've had the McDSP ML4000 for about six months and have found it a useful plug-in overall. The plug-in is easy to use as it has four knobs, one of each controls ceiling, threshold, knee, and release. The metering is great and monitors the input level, the output level, and gain reduction. The sound quality is clean and is easy to get a quick, effective level from this. Since I got this within a bundle, it was dirt cheap. I have come to love the McDSP suite of plug-ins as they are reasonable in price and all have a great sound to them. I would recommend this plug-in as well as the entire McDSP Project Studio LE bundle.