I've had my Harman Kardon 3600 for a whopping 5 days now, and so far it's been fun to play with. I'm still waiting for my first HDTV to be delivered so right now I just have it plugged into a 15-year-old 27" TV.
For speakers, I have a pair of Snell E2's (circa 1989) and a pair of Mission 762's (early 90's...I think). My old receiver was a Carver AVR100 (also 1989) but it died earlier this year. It's hard for me to compare how my Snell E2's sound with the HK versus the Carver, but I *think* it sounded better with the Carver, but not by much. It's hard to tell because it's been 6 months, but I'm pretty sure the Carver had better mid-range and wasn't quite as sharp on the high-end. Don't get me wrong, the HK 3600 sounds great, I just think that my old Carver complemented the tonal qualities of the Snell's (or reduced its flaws?) better than the HK. Of course, all my current listening has been with the EQ off, so I've got that to play with.
On another note, I have to say that the HK's on-screen menus are nice. And as mentioned earlier in this thread, it lets you completely customize the setup of all your input sources. With all the switching and changes I've been making, I haven't had a single pop, dropout or other anomaly...though it does take a second for the signal to change when I select a new option.
So far, my only disappointment has been with the build quality of the unit itself. While it has some heft, the metal is thin and the front panel buttons are plastic and not very sturdy. It feels as if you could accidentally break them if you push too hard, or if you use them a lot they would start to "sag" and not fully snap back. Not a big deal since I'll mainly use the remote, but I think I was spoiled by my Carver—that thing was built like a tank and all the controls had a solid feel. I've never had a Harman Kardon before, but I expected a better build quality from their top-of-the-line receiver.