It doesn't seem to operate as fast as when it was new. Loading webpages seems to take much longer than before.
Kind of tough one to answer because you aren't very specific.
One thing you can do is down load and run
OnYx to clear out some caches that have probably built up in the past 17 months and run some general maintenance. This is a widely accepted tool on these forums and is easy to use, free and and does a pretty good job!
Another thing is check to see how much available HD space you have. OS X likes a minimum of 10-15% available space.
Last is how much RAM does your iMac have? If you are in the habit of running multiple applications simultaneously that all eats RAM. RAM upgrades usually improve performance too.
Regards,
Roger
