I own ColorMunki Photo, and I'm GENERALLY happy with it. As simple as it is, I found that I still had some issues with it.
First, the software hasn't been updated since 2009. Not that it doesn't work, but it includes an ancient, security hole ridden 32-bit version of Java. There's a non-obvious workaround, you have to cancel out of the install when it asks about Java, and then you install your own version. Seems to be ok.
As far as display calibration, there's a night & day difference between the before calibration/after calibration.
Print calibration took me a little while to figure out, because I didn't realize that the pouch can't be used during printer calibration. It also takes a long time to do, because each test print requires a lot of drying time to pass the sensor smoothly.
Once I got the print calibration done, the before after difference was quite subtle on my Epson Artisan. Your mileage may vary.