I think I need to re-install Lion. Is this my best option for my computer?

Question

So, my late 2008 Aluminum MacBook has been running like the pits lately. It takes anywhere from 2:55 to 3:30 to start up with no Apps opening (Thank you 10.7.4), and opening any application, like Chrome for example, takes 16 bounces when opening the first time. I get some lag here and there too.
I have run Onyx, I have run Disk Utility to verify and repair disk permissions, I've even downloaded a couple anti-virus programs to see if that was slowing me down. I reset the PRAM, SMC, PMU, and I think the next option is to do a clean re-install of Lion.
I've backed up my computer every other day for the past week in preparation for this. My MacBook has 4gigs of RAM and over 100Gigs left of storage on its HDD.
Should I re-install Lion? Should I do anything else first? My thinking is to restart the computer into the Recovery HD and then just re-install Lion. A question is, will I have all my files still on the computer, or will this wipe EVERYTHING clean? I'm just lost, and don't know what to do. Help!

Answer 1

I would consider:
Repair the Hard Drive - Lion
Boot from your Lion Recovery HD. When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list.  In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive.  If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported then click on the Repair Permissions button. When the process is completed, then quit DU and return to the main menu. Select Restart from the Apple menu.
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
Then download and reinstall the OS X Lion Update 10.7.4 (Client Combo) updater. See if this resolves your issues before undergoing a reinstall.
BTW, most of what you say you've already done should have been done before you updated to 10.7.4, so don't be so quick to blame everything on the update. It might have been the updater.