To stay up-to-date with all the latest bugs, interim fixes, fix packs and new releases, monitor the IBM Tivoli Software Support RSS feeds:
IBM Software Support - RSS Feeds
For the Netcool/Impact RSS feed, look for "Tivoli Netcool/Impact" on this page. Note that there are feeds for OMNIbus, Reporter, Webtop and others.
The easiest way to monitor the feeds of your choice is to use an RSS feed reader client - like Mozilla Thunderbird. I find it works well!