With ArcGIS 10, turning on the option to display the number of Features on the ArcCatalog Contents tab severely cripples the performance of ArcCatalog. Knowing the number of features in each layer is a very important, fundamental thing - it is not optional in any way. I need to be able to see and compare feature counts in multiple feature classes in multiple geodatabases very quickly. I encourage Esri to figure out how to maintain and display this information quickly and dynamically, without crippling performance.
This is what you have to do in ArcCatalog to display the number of features: Customize > ArcCatalog Options > Contents > Metadata columns > # of Features
The only problem is that the performance will be Extremely ainfully slow if you do this. It should be instantaneous.