I've just started using Java on Eclipse (Juno) after a 15 year break from Java. I was using the ADK on a 1.6GHz Atom N270 with 4Gb RAM on W7 32bit on a nearly empty disk. Not sure if it is the Atom or whether Java is as bad as it used to be 15 years ago but it takes over 2 minutes for Eclipse to even start. The emulator does turn up eventually but is extremely sluggish. Even without the emulator, Eclipse is sluggish.
On a 1.6GHz Core i7 or a 2GHz Core 2 Duo, operation is reasonable. Emulator works, Eclipse takes about 5 to 10 seconds to be ready for work. Moral of the story: don't use an Atom or any other low powered processor. It is sluggish even with 4Gb memory and having the same clock speed as a high end processor.
I've also tried it in a VMWare VM on the 1.6GHz Core i7 and on the Core 2. It is reasonably fast until the the emulator is started. It then slows down to the point of no return. Redraws is now very much like that of the Atom but at least it responds when the buttons are clicked. Note that it is now running an emulator within an emulator. The only problem with VMs is that every so often W7 does what W7 does. There is a wait cursor and whole machine is totally unresponsive for a minute or two then it springs back to life. This was with VMWare V3. V4/V5 might be different. Varying the number of cores/processors did not make any difference to eclipse or the emulator.