If a game has loads of small files eg: SM II the launcher is very slow at checking hashsums.
A great solution would be to make the process multithreaded.
The same thing can be done with downloads (for gui sake a drop down tab with the progress bar for each download thread can be also added ).
Options for these should be avaible to the user in the options tab as a lot of programs allows this kind of feature.(Maximum limits for these options may be setted to 8 deafult can probably be 1 for download and 2 for hashsum.)