I found it really difficult to find a memorable theme. The music seemed okay in that it did its job well, but I felt that so much potential themes or motifs are missed out on.
Jack and Sam could have had a decent theme.
There could have been a menacing "storm's brewing theme".
A theme or motif for the actual storm sequences.
The freezing eye of the storm thing could have had it's own theme.
There could have been a more heroic theme to be played when Jack first meets Ian Holms character, replayed when Ian Holm's character and co. face thef act they are going to die (but more somber) and again whenever Jack does something heroic and at the end when they see all the survivors.
I'm not saying it was a bad score, but I felt thematically it was lacking.