I would choose the 520 in a heartbeat over the 676, 688, and 880.
I've gone through a number of remotes in the past 5 years (Pronto, Sony V1000, HTM MX-500, RTI T2 URC-200, and variou Logitech Harmonies) and I've come to two conclusions:
1. The most advanced remotes with software programming for multiple system components (no matter have intuitive the software is) don't mean d**k if ONE DOESN'T HAVE TIME TO PRORAM it (working professionals, you know what I mean). The Pronto fails miserably in this criteria. The RTI T2 has an excellent software program but it still took time and had a problem with ergonomics (see item #2 below). This is why I love Harmony's online programing -- it took me 20 minutes to program my Harmony vs. the 5 years of fiddling around with these other "sophisticated" remotes.
2. Unless you are a turn it on/leave it type of A/V enthusiast and not a channel surfer, HARD BUTTONS and ERGONOMICS are KEY requirements to enjoying the remote. The Sony (the slim line, not "AV" line) and HTM/URC remotes excel at this; however, they do not have the superior software programming vs. the Harmony. The Harmony on the other hand does not have the ergonomics nor tactile feel of the Sonys and HTM/URCs. The 880 has poorly placed hard buttons. The 676 does have separate the buttons (vs. 688) but one STILL must look at the remote to see where the buttons are; the volume and channel buttons are incorrectly placed in the lower half of the body -- an odd place for the thumb to press. The 688 is perfect ergonmically in a sense that all the most used buttons are placed where the thumb than naturally reach; it's only shortcoming is the buttons are tightly compacted and the directional center button is not the most tactile.
The 520 -- from detail views (
[Link: assets.logitech.com]) seems to address the ergonomics issue I have with the 6xx and 8xx series. It reminds me of a slick Sony remote combined with a good layout of HTM/URC.