I have the Magic Wand in the neon yellow color, and I like it... when I use it. I don't use it often because I seem to prefer marking a single line diagonally on the back one square and sewing ~1/4 inch away from that. I also have a
Quilter's Rule Quick Quarter II. I purchased it a long time ago, and unless things have changed, I'd skip it. Mine has rough edges (so my line isn't as smooth as I'd like) and isn't as easy to use it's hard to line up the center line properly.
I liked the Magic Wand because it's clear of markings other than a thin groove down the back (and the brand name in the middle, well out of the way), which is what you line up with the corners of the square. It's also long enough to use for pretty much anything I'd be making. It's just not something I use often.