Q: My iMac is running slow on all applications. Is there a program or utility I can use to improve performance? Are there memory or other limitations I should be aware of? I do not use MacKeeper.

DO NOT download or install any third party utilities to improve the performance, they simply are not needed. What you need to do is find out why you computer is acting the way it is.

I would recommend running an EtreCheck Report and then posting it for us, then we can tell a little about your computer and look to see if there are some bottle necks. It is possible all that is needed is a RAM upgrade. If you are in the habit of having a lot of apps open at the same time and lots of tabs open on your browser at the same time that all uses RAM. If you use the base 4GB of RAM then that could be the issue.

To download EtreCheck please click http://www.etresoft.com/etrecheck

I have a 24" 2011 imac and I had the same issue. Don't even try to open more than one media window, or edit a movie. I found that while browsing both browsers (safari and firefox) would freeze and then when I went to close it or even tried to open finder (to open activity monitor) my whole comp would freeze. Only way I could do anything was to shut down w/ the power button. When I tried to restart about 1/2 the time it would hang on the apple logo, I'd get the time clock rotator thingy, it would disapear then nothing...forever, til I'd repeat the power button sometimes 3-4 times before it would start. I don't use tabs, and it would freeze with only two or three windows open (same power as 3 tabs I'd assume).

I had nothing but issues w/ mavericks. I found not one real benefit over Snow leopard except maybe icloud support.  I'm back to Snow Leopard and my comp is working like a champ, starts up in less than 1 minute (closer to 45 seconds) from a cold start and media is fast as ****. I thought my connection was slow, but it was the o/s.

I only have 3gig of ram and my comp was running at about 80% full on the HD.

Warning: If you decide to go back (like so many others with older comps) you can't. Not without reformatting your HD. You can't use time machine to backup your stuff. You'll have to save all your files individually to an external HD, then place them back once you've erased and installed the older o/s.

I spent a few months trying to figure this out. It was a waste of time. I'm sure w/ a faster computer and more ram mavericks is great, but since I doubt you have more than 3gig of ram (mine won't recognize 4 gig when I installed more ram, only 3, it wouldn't even work w/ the extra memory in.

I'd recommend going back to the o/s you had before instead of banging your head against the wall with an older comp and mavericks.

See:

Mac Maintenance Quick Assist,
Mac OS X speed FAQ,
Speeding up Macs,
How to Speed up Macs,
Macintosh OS X Routine Maintenance,
Mac troubleshooting: What to do when your computer is too slow,
Essential Mac Maintenance: Get set up,
Essential Mac Maintenance: Rev up your routines,
Maintaining OS X, 
Five Mac maintenance myths and
Myths of required versus not required maintenance for Mac OS X for information.

I'd recommend going back to the o/s you had before instead of banging your head against the wall with an older comp and mavericks.

I'd recommend fixing your own problems rather than recommending unhelpful actions inappropriate to rep64's concerns.

I have a 24" 2011 imac and I had the same issue.

No you don't. Please start a new Discussion.

When you next have the problem, note the exact time: hour, minute, second.

If you have more than one user account, these instructions must be carried out as an administrator.

Launch the Console application in any of the following ways:

☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad. Click Utilities, then Console in the icon grid.

Make sure the title of the Console window is All Messages. If it isn't, select All Messages from the SYSTEM LOG QUERIES menu on the left. If you don't see that menu, select

View ▹ Show Log List

from the menu bar.

Each message in the log begins with the date and time when it was entered. Scroll back to the time you noted above. Select the messages entered from then until the end of the episode, or until they start to repeat, whichever comes first. Copy the messages to the Clipboard by pressing the key combination command-C. Paste into a reply to this message (command-V).

The log contains a vast amount of information, almost all of it useless for solving any particular problem. When posting a log extract, be selective. In most cases, a few dozen lines are more than enough. It is never necessary or helpful to post more than about 100 lines. "The more, the better" is not the rule here.

Please do not indiscriminately dump thousands of lines from the log into this discussion.

Important: Some private information, such as your name, may appear in the log. Anonymize before posting.

Please post the complete report, the report you posted eliminates a lot of vital information.

What OS version did you upgrade from? DId the slowdown occur immeidtaely with 10.9?

You have plenty of power, and, frankly, i found 10.9 to be close to as fast as 10.6.8 (whcih in my experience was faster than 10.7 or 10.8).  I dont see anything aggregious in your entrecheck, but then, i dont know every app's interaction.

Make sure all your 3rd party software is up to date.

Your RAM looks like it is not being over-taxed, and your CPU is mostly idle.

Vitals look good, patient still sick, i know.

Grant