For performance issues, there are a few things you can check:
Check your Login Items under System Preferences > Accounts to see what you have automatically launching.
Also check /Library/LaunchAgents/ and /Users/yourusername/Library/LaunchAgents/ for items launching at startup
Look at what widgets you may have running.
Launch Activity Monitor and change "My Processes" at the top to "All Processes". Then look to see what may be consuming system resources.
Take a look at the System Memory tab at the bottom of Activity Monitor to see if you have excessive "page outs", a sign that you may benefit from more RAM.
Make sure you're not running any 3rd party antivirus app, as many of those will drain resources, reducing performance. They're not needed to protect your Mac.
Lion is proven to boot slower than SL. (There are some proven benchmarks on this somewhere).
But... not twice as long... maybe 10 seconds or so. It's not clear of course whether those benchmarks are measured to Lion's desktop or when the OS is actually usable (i.e... it depends on what Lion is restoring from the last session).
I also suspect that many people who find Lion booting faster than SL is because the upgrade cleaned out some clutter from their old system.
I couldn't tolerate all the disk activity in Lion so I also upgraded to an SSD. Subsequent OSX releases from here on will depend more and more on solid state memory so it's a losing battle.
I agree too, I upgraded my hdd to a intel 320 ssd, and on start up with SL I would only see the Apple logo and the little spinning wheel only turn once. With lion I definitely see the inconsistency of boot times, varying from 2 turns up to 15!!
Other than the initial boot time, sometimes I notice a long hang on shutdowns as well.