1. You can but I believe you're going to need an external mouse/keyboard to wake it (computer sleeps with lid closed but you're aware of that)
2. Much discussion about this. It will run a bit warmer but will probably run maybe 5 degrees higher? It's not a lot so don't worry about heating issues.
3. I'm not someone who works with cinema displays or any other displays of that quality but being around one I can tell you that it is beautiful. Everything is so rich and crisp. Now, I don't know your financial positions but are you sure you need an ACD? If you're someone who is working on projects that require you to use something ACD caliber, then I guess it's an option since those types of displays are generally the same price but if you don't, I would suggest you pick up any other LCD screens such as a Dell. Images are great and much more cheaper.