Quite addicting!
This is a great game. As my title suggests, I spent a lot of time in front of the screen (and I'm sick, damn it. I shouldn't be doing this. =p).
No point on complaining about Madagascar, since everyone and their dogs have done so. Although, there are a few areas I also had trouble with (like Indonesia and Australia). The music is a bit monotonous, but you cannot really expect something active on a game like this, so I guess it fits.
Anyway... My one and only complain is regarding the vaccination. I don't know if it's a programming error or if you did it on purpose, but.. When the vaccination is completed during the first time and found useless after being deployed, the development bar is restarted but not the deployment one. So, after the vaccination is developed for a second time, you don't get a message about its result, since the deployment bar is still full. And apparently, it takes it as a successful try all the time, because all of those times I saw the amount of healthy people on the same numbers.
And, well, that's my onlt complain. Other than that, great game! I'm not going to be happy until I can wipe out humanity.