This movie didnt ever get much attention, perhaps only getting what it did via those who had read the book. So I wasnt expecting a great deal to be honest, but I actually had a great time. It is a fun family-style adventure when managed to build enough tension to keep me watching intently throughout. I liked the soundtrack as well by Andrew Lockington, though it doesnt seem to be on iTunes for me...
There are plenty of effects shots of various types which are used to flesh out the future-city of Ember, in its rundown and rustic state. The main use of the effects is in pulling off the many action sequences.
[Promo images from City of Ember from the main site via IGN]
City of Ember site