Alright, since I just went through the same thing I'll try to offer an opinion as well. I was in the same situation with gift cards available for BB, so when the Harmony 880 went on sale for $145 I decided to buy it. Of course when I brought it home the first thing the wife asked was "how much was it" (we've been stuck with two homes for a while now, must be budget conscious...). She couldn't believe they sell remotes for that much, anyway....
The 880 was nice, color LCD was nice, not a necesscity but nice. It worked well, but I had a few concerns. I didn't like the buttons, I always felt like I was hitting a couple of buttons instead of just the one I wanted. I also had a problem with the play button not working with the dvd player, but everything else was fine. The 880 comes with a rechargeable battery and cradle. I have heard of a common complaint where the remote doesn't sit on it well and doesn't always charge as expected. I think I ran into this issue as I left it on overnight and the battery hardly had a charge the next day. I charged it for another 24 hours and a day later the battery's charge was down a thid already. I did not like the idea of leaving the charging cradle plugged in all the time, and wasn't sure if the charge would last for weeks at a time as I would expect.
On the other hand, there were a couple of things I liked. The LCD was bigger, so if shows 8 items to pick from instead of 4 like on the 550. I don't like having to scroll 8 screens when I need to change a setting on the tv or receiver. Also, the 880 had the time on it. Call it cheesy, but I haven't gotten a clock of any kind for my room, so it was nice to have it there. Oh, and the remote lights up when you move it, that was nice too. However, I decided the shortcomings outweighed the good, and for over $60 cheaper I went with the 550. No big complaints with it other than the smaller LCD and no clock. I have lots of rechargeable AAA batteries so I don't mind not having a charging cradle. The 880 was good, but not where I would like it to be to justify the price, the 550 is a good compromise.
For anyone still looking for a 550, CC has them for $79.99 this week (Adameus, if you're still looking). Also, if anyone has read this far here's your prize-
http://bundleup.logitech.com/index.php
I think that still works, play the game, and after you lose you'll get an email with a link to a 10% mail in rebate to Logitech for a remote purchased this month. Hope that works still, if not let me know and I can probably get a link to the rebate itself with the rules. Good luck.