Please note that I managed to fix both the boot and the shutdown time by uninstalling some applications not currently compatible with Lion, WITHOUT A CLEAN INSTALL!
I tried the cache cleaning trick using iTweax, but the shutdown time was still horrible. My boot time was close to 1min30
I read in another thread that someone deleted old applications not compatible with Lion and it solved their issue, so I tried it.
I uninstalled Mac The Ripper, which was not compatible with Lion (the app was "hidden" inside a sub-folder and it was missed during my day-1 Lion cleanup of all the apps bearing the "not compatible" icon). I uninstalled Gimp! which I don't use anyway.
Note: I erased all related files using the very good App Cleaner software which finds and lets you remove everything related to an app.
I tried to shutdown again, though I had Skype and MSN Messenger on, and those slowdown the shutdown process with all the questions "are you sure you want to terminate this chat session". Still it was very fast, no beach ball and no hiccups.
The boot time is now 52 seconds up to the login screen. This used to be my shutdown and boot time together before Lion.
Running Mid 2009 15'' Macbook Pro 2.66 GHz, 8GB RAM and 640GB 5400rpm Toshiba HDD.