Portal 2 is an enjoyable experience and definately betters itself from the first. On a side note Portal 2 does seem to over use game mechanics whenever a new one is introduced rather than mixing it with the others and some of the original mechanics such as turrets seemed to be overshadowed. If you can look past some of the terrible level design at points it's worth your money, no questions asked.
Wrote a review/recommendation on Steam.
Also don't even bother arguing about me with the level design, there was some pretty crappy parts with the map.
Such as when you have to position and pivot yourself at a certain location and angle so you can see the corner of a panel above you that you would have never noticed.
It's suppose to be a puzzle game, not find waldo.