OK, so I've had the Harmony 768 remote since last Sat. The components I control are:
old 27" Zenith as a monitor only
Pioneer 45TX A/V
Apex AD-600A DVD player
Proscan VCR
Sony SAT-T60 DirecTV
Initial Setup
I've played w/ the online tutorial and it seemed pretty easy to set up. You go to their website to configure your remote according to your components and then your remote is updated w/ the configration. I installed the software from the CD and tried to download to the remote but the firmware and s/w needed to be updated, which I did relatively easily. Now I can go to my online account and add/remove activities and devices and just connect the remote to my PC to update.
Impressions
Different. Not bad, not IMPRESSIVE, different. I'm used to hard buttons, I also use the URC6131 that is GREAT w/ Tivo. 2nd only to the Tivo remote which I think is one of the best ergonomic remotes. The Harmony is different because it's activity based, not button based, so for me it's a "culture change". You don't press buttons/macros, you choose an activity and it runs. To watch Tivo, I select the "Watch Tivo" activity and the system (1) turns on the TV, (2) turns on the A/V, (3) sets up the surround mode on the Pioneer, (4) turns on the Tivo, and (5) set the channel to my favorite channel. I have activities to watch the VCR, listen to the radio, watch DVDs, etc and all the macros are set up to control any required component.
The setup is "relatively" flexible because you and add menus, activites, reassign buttons, create macros, etc. You can also edit existing activities to add more "button presses" to it, which is what I did to set up different surround modes for each activity. For example, when listening to the radio, I set it to 5 channel stereo. I say relatively because it also allows you the ability to use XML to add/modify the actions of the remote. Almost too flexible, because most users may not want to deal w/ the hassle. But when playing w/ the remote, it may be worth the hassle because you can create your own complicated macro once you learn the method.
I haven't let my wife play w/ it yet, I want to get it close to perfect so I can get the best acceptance.
But my initial impression is that this is a VERY powerful remote, provided you are willing to do some tweaking. I get the impression that would also be the case w/ the MX500 & MX700 too. The activity based concept may work better, though, w/ the others in your family who don't want to press all the buttons on various remotes.
Regarding Tivo, that's been the toughest to set up. For existing PVR owners, you realize the importance of all the hard buttons. The 768 doesn't have quite enough, but it's possible to configure it to access just the right amount and then also create single button macros to assist w/ the menu searching. The newer 659 may work better for those who really like the hard buttons. One nice thing on the 768 (and not on the 659) is the ability to have the TV Guide on the remote, just like the directv guide. Longer downloads, but pretty slick. You select the show according to the current time and the remote selects the correct channel.
Hope this is helpful and perhaps I'll add more as I play w/ it.