The "timebomb" although sounding dramatic will, I'm sure just act like a normal end of a trial period with an OS or any other software. You will get warnings when you log on that you have x days before the trial ends and if you ignore these the OS will go into a reduced functionality mode which will allow you to save data but not create anything new.
Whist saying this I would advise everyone to remember this is still a Pre-Beta software for evaluation
. It should not be used as your main "Production" OS, even though it's the most stable of any I've seen, It could still fail at any time causing loss of all data on it's partition.
If you are using Windows 7 as your only OS please make sure you back-up all of your data as often as possible or at preferably save your data to another partition.