For long time bloggers has been spending money/searching for codes for a better designer templates ,as because the layouts in the provided templates were fixed.
Using template designer, you can now not just alter position of widgets in the layout but also alter layout position and number of blocks to add widgets .
you can also change font ,background ,colour, width of main post body , width of sidebar ,background images provided,Custom blog layouts with one, two and three columns
also most importantly when shift to new template your previous widget don't get deleted and also you can always preview changes before applying changes
The only thing that you may not like are attributers at the bottom which you cannot remove