My iMac is running extreamly slow with OS Lion! Help ?

Question

My iMac is running extreamly slow 24hours after installing OS Lion! I don't think it is the Hardware as it only slowed down after it crached 24 hours after running fine! Help ?
My iMac is 3.4GHz Quad-Core Intel Core i7 8G of Ra

Answer 1

Same here. It's horrible. I'm using "fast user switching", but "fast" is not really the right term for it. More like, "excruciatingly slow user switching". It can take up to 15 seconds after I click the menu to switch users (from one logged-in user to another logged-in user) before it prompts for the password!  The load average is 0.77 - 0.84 and there's nothing running that is taking more than 9% of the CPU.  So it's just insane. Makes no sense at all.
I tried watching a video in QuickTime player, and it would play for a bit, then get *way* behind -- including delaying my controls/commands to the player.. I.e., it would pause for seconds at a time, during which I will have hit pause/play a couple of times, then maybe using a 2-finger swipe gesture, tried to scrub the video forwards/backwards. The video would have frozen during that time, but once it unstuck, it would do whatever things I'd asked it to do many seconds earlier, in sequence, with freezes in between.  While doing this, hitting "quit" (command-q) seemed to have no effect, until it finally caught up with all my inputs and finally quit.  I mean, this is crazy stuff. It makes no sense at all.
It's so slow, as to be entirely useless except maybe for web browsing. But actually using the machine? Not really going to work. I can't have people go up to the machine and click the user they want to use in the fast-user-switching menu, and then start to type their password only to have the text they're typing just show up in whatever app is currently active (whether it be finder or a program that actually lets you type, like Terminal). I can't understand how this could be so bad, especially given the load averages being so low and nothing hogging CPU.
  Steve