It takes a long time to load the home screen Returning to home screen after sending an SMS or making a call takes up to 7 seconds on an average where as it used to be much faster six months back. Its a Aug 2011 model. System hangs often coming alive with Force Close application message. Why?
Because Sammy's software is buggy! If yours is a galaxy S i9000, then there are ICS Roms on XDA forum which I found far smoother and usable on my phone than Samsung's touchwiz Gingerbread.

If you don't want to go through the hassle of rooting, flashing a custom ROM, then I suggest that you backup your data and do a factory reset. 

settings=&gt;privacy=&gt;factory data reset