lots of people use solid drives as their system drive yes... the C drive is where Windows is installed and normally you want that drive to be as fast as possible but older drives don't cost as much so they make fine storeage
worth getting = about 250G is where most laptop users like a c drive +[at least] 500G for a system that does editing or needs to run on battery while you travel = yes worth it
i personally like the 120G solids for my laptops and I shub a 1-2T storage drive too which does everything i need at less than 1/2 the price