If you're looking to connect your devices to the new 27" ACD's via the MiniDisplay Port then I can offer a bit of input. I also spent a fair amount of time trying to connect my devices to my old 30" ACD, but every setup I tried was unacceptable.
For all intensive purposes I'll list my living room setup and the setup that I created for my office to mirror my living room setup as closely as possible.
Living Room:
• 55" Samsung C7000 series LED TV
• Bose Lifestyle 48 Series 3 Surround Sound
• Xbox 360 Elite (Gen1?) -- it's the previous generation of the Elite
• Playstation 3 (Gen1)
• Nintendo Wii
• ATV Gen1
• DVR
All devices, aside from the Nintendo Wii, are connected via HDMI
Office:
• 27" Apple Cinema Display
• Atlona AT-HD620 ::
http://www.atlona.com/ATLONA-HDMI-MINI-DISPLAYPORT-TO-MINI-DISPLAYPORT-SCALER-AND-SWITCHER.html
• Atlona AT-HD41D 4x1 HDMI switch ::
http://www.atlona.com/4x1-ATLONA-HDMI-DIGITAL-AUDIO-SWITCH-HDMI-1.3-with-3D-Support.html
• Bose Companion 5 ::
http://www.bose.com/controller?url=...stems/computer_speakers/companion_5/index.jsp
• Xbox 360 Elite (Gen2?) -- it's the current generation of the Elite, but the Gen1 will work just fine as well.
• Playstation 3 (Gen1)
• ATV Gen2
• DVR whenever I decide to go pick up an extra.
All of the devices are of course connected via HDMI with the audio being output from the HD620 and hooked into the Auxiliary port on the Companion 5.
My goal when I started out with this little project was to mirror the setup that I'm using in my living room as closely as possible and with the least amount of picture quality loss. I was willing to sacrifice a little bit on audio as I didn't believe a 5.1 surround sound was necessary for my office.
I've had absolutely zero issues with pixelation, response time, stretching/warping, compatibility etc etc. Sure, I'll agree to the ACD lacking in ports, but that hasn't been an issue for me at all. I had the HD41D laying around from my previous TV that didn't have enough ports, so I just hooked that into my setup. Blu-ray (PS3) looks amazing -- no issues there. I only play Gran Turismo 5 and Final Fantasy 13 on my PS3, but they also look amazing and there aren't any issues with those games. The majority of my gaming is spent on the Xbox and I've yet to run into a game that has any issues -- the list of games that I've played on the Xbox through this setup is pretty long, so if you have a question about a specific game feel free to ask.
All in all I'm extremely happy with the end product and to be perfectly honest, the only noticeable difference is the size of the display that I'm looking at. Sure this setup wasn't exactly cheap, and I could've bought a LCD TV for less, but I decided that I wanted my secondary display to match my primary.
If you have any questions about my specific setup feel free to ask. However, I can't offer any input on the other monitors (i.e. the Dell) since I have no personal experience with it/them.