I wouldn't worry about it. You can always use Disk Cleanup (just type it from the Start screen to find). You can also view how much space your apps are using by going to: Settings > Change PC settings > General > Available Storage > View app sizes
Windows RT, windows 8 metro in general, handles this very well. It may seem instantaneous but likely some work is being done in the background. I've been very impressed how this first gen product delivers.
You have to clear the cached uninstalled apps in this location:
C drive
windows
Software distribution
download
Right click and click delete and all the uninstalled apps that have been cached ( Which are ALL of them) will be removed. I do it every month or so and it removes 6-7gb. Good luck