As of the 29th February 2009 the IOS Upgrade Planner will be retired and replaced with the 'Download Area' similar to the Voice Download Area. I am not a big fan of the download area layout as it can be sluggish and moving backwards resets everything meaning you have to select everything over again. However its changing so I will have to get used to it.
One thing I have noticed is missing software in the Download Area for the Catalyst 3550. 12.2(44)SE5 is the latest available via the Download Area, however via the old planner 12.2(46)SE is listed? Is this a mistake or is it by design?