SSD will be very helpful in near future,There'll be games of larger size which take lot's of time to load at the beginning.
SSD will ease that problem up.But their capacity is less and price is too high right now.
If SSD's get cheaper in a year or so,buy a SSD of about 500GB,then use it has a C drive,you know what i mean.
It's like storing all the system data, The OS and app programs,even install games in that drive,it helps to load faster,
In HDD you store movies,music,documents,installation files etc...