There used to be a way to demo the Harmony setup site and set up all your devices and activities so you could get a feel of what was possible and what might not be there yet for your equipment. A quick scan through the site left me unable to find it now though.
I have a Harmony 520, and I love it. For those occasions when I'm a/b-ing gear or playing with new devices I keep a couple of the remotes in a drawer in a table next to the couch, but that is rare that I need them. My wife would be unable to use the system at this point without the 520, and she really is happy we got it, although at the time she was pretty skeptical about paying nearly $100 for a remote.
One thing to be mentioned: all the harmony remotes run the same software and do the same things. The difference between models is mostly button layout and number, and the more expensive ones can control more devices, although even the 550 controls up to 15 devices.
Ah! here is a link to do a test drive with the 550:
http://members.harmonyremote.com/EasyZap...tType=TestDrive If you end up getting a different harmony model, you can use the same account, it will just discover the new model when you first try to download the software, then change all the images on the site to look like the other remote.