I LOVE the 4½" grinder, with flap wheel, grinding disc and slitting disc, the guys I worked with a few years back when I was messing about with Hovercraft used to refer to it as my 4½" lathe.
Bob, you're right about the 1mm discs, you have to treat them with respect or they shrapnel in a big way, don't side load them and don't try to polish welds with them either. If you drop the grinder they shatter pretty easily too. Using a 1mm disc to chop through wood, when nothing else will fit in the available space, the smoke is amazing, ask me how I know.....
It would be nice to have a plasma cutter, but I can't, yet!, justify the expense of a big one and when I used a small one, some while back it's true, I wasn't very impressed.
Cheers
Stef