KillerJuan77: I want to get it but not if it's nightmarishly difficult.
The original Constructor is very difficult. It's not only that the game is very fast paced and requires a lot of micro-management, it is also an old UI that lacks a lot of features that you would expect from more modern interfaces. The most obvious is the lack of an active pause (though that's not present in Kalypso's more modern games). So you have to be constantly checking up on everything, and being very methodical.
The game has frustrated many because of its difficulty, if you can get passed that then it's good fun. If you choose to go with it then there is a thread "Tips for constructor" which highlights some ways that allow you can tune the difficulty a bit.
I can't comment on Mob Rule, haven't got round to playing it.