I too have a laguna 2 Dci Dymanique with 67k on the clock. (2004 04 plate)
I am getting 47mpg at the moment but mainly longish runs but Iam light on the pedal.
A couple of niggles on my car the electric passenger window refuses to budge unless you give it a helping hand (will get that fixed when i get round to it) and the stupid xeon lights that self adjust - too low for my liking but will sort that again when i have time.
Ok not as good on juice as my Smart car or £35 road tax but it is nice to drive and i can get my fishing gear in (no way would i get that in the Smart) all in all am happy with it.
One thing to bear in mind, I always join either news groups or forums when i buy a car and yet I have to find a forum that everyone says there car is fantastic, thats not what forums are about, its all about helping each other with problems.
Stick with the car you will get to like it.
There again I used to love my Hillman imp and my Isetta bubble car