I used to be more concerned about excess noise at higher ISO settings but now I really don't anymore. I recently purchased a Sony F828 and at higher ISO settings it is noisy but this program called
Noise Ninja really cleans things up well without losing quality in the image like filters in photoshop and others do. It's pretty fun to play around with too because of how clean it makes things. It takes a bit of playing around with to get used to it but once you get a good grip on how to use it, it becomes a great tool in your digital photo software arsenal.
The link for that program is
http://www.picturecode.com