I have had a MX500 and MX800. The 500 wasn't programable by computer and so you had to go through a series of steps to create macros which was a real pain in the you know what, but I really liked it's layout (at the time), so I upgraded to the MX800. This was great for a year or two until URC became real jerks to their customers and stopped allowing us to download updates to the software, and effectively gave us a last update which could no longer connect to pull down newer device codes/settings, essentially requiring us to now learn every button and combination of buttons from the device's remote. I simply can't recommend them anymore to anyone unless you have a sales rep which will give you the real software to update your remote (many will not do this).
I switched to the Harmony 880. I have 2 Harmony 880's and a Harmony One. I wish the One simply had hard buttons on the side of the LCD and not a touch screen like the 880/890's used. My 880's are starting to have problems with the volume buttons (like just about everyone else). I would get 2 more One's, but they are harder to find now (or cost $300+, when they were down to $100-150 retail).
I can't stand the current Harmony Touch, Smart Control, or Ultimate. You should NOT NEED TO LOOK at your remote to use it!!! There are NO NUMBER BUTTONS for changing channels!!! This means you need to flip through your TV stations to get to the one you want, or program macro's for every station that you watch, which is ridiculous, or need to flip back and forth between 2 pages on the LCD to have programmed custom numbers for 0-9 since you can only fit 6 on the LCD screen at once! The Harmony 650 simply can not control enough devices to be useful to me (I have had remotes from cable/satellite that allowed me to control more than 5 devices!!! My setup needs 9 devices, and over 12 activities), and the 4 boxes/items on the LCD is pathetic. It should have a MINIMUM of 6 if not 8, otherwise you have to go through dozens of pages for some types of devices to list all the functions which do not have a dedicated hard button.