Well, technically it's not an emulator but a virtual Machine. In the end that doesn't matter though. :)
Bluestacks lets you run almost any Android app or game on your PC. I killed a lot of time with Drag Racing and Angry Birds Space. :) If you need some kind of multi-touch controls try experimenting around with the keyboard. A lot of standard user interfaces seem to be mapped to the keyboard. That way you can use keyboard and mouse like you would anyway on a PC.
At this time it's still in beta but already runs like a charm. It crashes maybe once a week but I'm sure that's not as annoying as real phones telling you that their Battery is getting low.
Until it is officialy released it's completely free to use. After that it will cost some money but it should still cost much much less than a new Tablet or Phone.
If you want to give it a try you can download it here.
Should you own a Mac and be interested, the developers have said they're working on a Mac-version as well.
All in all I'm really excited about this and I'm looking forward to the actual release.
If you want to get in touch with the team behind Bluestacks you can do that best over Twitter at http://twitter.com/#!/bluestacksinc
You will probably see that a part of Bluestacks, the RocketDock, gets autostarted with Windows. Although I love Bluestacks, this thing annoyed me, because I found exactly no use for it. I got rid of it after killing the process "RocketDock.exe" and renaming the exe itself in "C:\Users\Your Name\AppData\Local\BlueStacks\RocketDock\" to "RocketDock.meh"
Other than that I can see that some of you could get annoyed that you "have to" login to Bluestacks with your Facebook account. Well you actually don't. You only need to do that if you want to synchronize Bluestacks with an actual android device you already own. Because I don't own an android phone I could not test the cloud functionality of Bluestacks.
If you want to change the path of the SDCard -file Bluestacks uses you can change that in the registry under "HKEY_LOCAL_MACHINE\SOFTWARE\BlueStacks\Guests\Android\BlockDevice\2\". There are other options you can fiddle around with, like the resolution of the Bluestacks window while it is not in fullscreen mode.
Also you should get yourself another launcher because the default one is at this moment a bit lackluster. I'm using the AWDLauncher.