Installing the Steinberg Magneto plug-in wasn't a problem at all because it installs itself when you install Cubase. I used to run Cubase SX 2.0 before I got my Pro Tools rig and this was one of my plug-ins I used within that configuration. Steinberg Magneto always ran smoothly and stably for me without any compatibility problems or other issues. I've never seen the manual for Steinberg Magneto so I can't speak to if it is helpful or not when trying to figure out this plug-in.
When I used this plug-in in Cubase SX 2.0 I was running it on a Hewlett Packard lap top that had a 3.0 Ghz processor and 2 GB of RAM. Steinberg Magneto and Cubase as a whole always ran pretty well with this configuration and while I didn't use this plug-in everyday, when I did use it I was able to run a few of them at once if I so desired. It can be used both as a stereo or mono plug-in.
I've been using Steinberg Magneto for about five years and while it wasn't my first choice for warming up a signal, it did work well for me when I found a place to use it. The plug-in is pretty easy to use as it has knobs for high filter, tape speed, drive, characteristics, input, and output. It also has a series of buttons to determine what will show up on the meters. Since the plug-in came free with Steinberg Cubase SX, I can't really complain too much about it, but suffice it to say that sometimes it doesn't always sound that realistic sounding. In other words, if you want to warm up your signal it is probably best to do so at the source or with your pre-amps or other hardware, as it is almost impossible to do so all the time with a plug-in. This being said, for those using Cubase, Steinberg Magneto comes in handy and is nice to have.