I think it's ageing quite well, and I definitely prefer watching it now that the hype surrounding it has ebbed away. It's better as a 'popcorn flick' than a disaster film I can take too seriously.
My biggest problem with it was the aformentioned hype. There were posters and billboards depicting a disaster movie that spanned the whole world... we saw the Sydney Opera House being engulfed by an impressive tsunami, Big Ben Clock Tower glistening from within 50m of snow, the Brandeburg Gate locked in ice. It was such a massive concept and ultimately one that the film couldn't live up to. In fact, it burns out about half way through its 2-hour duration when the most impressive scenes have all passed. The film worked to begin with by throwing disaster after disaster at you, but when this stopped (and the budget was capped) they had to turn to a human story which hadn't been very well set up and so I didn't care. The film would have done better if it had stuck to throwing CGI at the screen, at least in terms of consistency. Instead, the first half disappointed anyone looking for a film with substance and the second half disappointed anyone wanting any decent action...and nobody walks away complimenting half a movie.
The tornado scene was most impressive, the movie as a whole was a spectacle and a half, but it felt like they changed its purpose half way through and it just all fell apart from there.