The short of it: According to Intuit, the following versions of Quicken for Mac (Quicken for Mac 2005, 2006 or 2007) will not work on Lion. Only Quicken Essentials will work on Macs that are updated to Lion.
What alternatives does Intuit suggest?
1. Quicken Essentials for Mac. You can find more information here.
2. Try Mint.com, an online finance management service.
3. Use Quicken for Windows. (Not one of my choices.)
There are other Mac based options that I will highlight here in the next several days. Suffice it to say today: if you need/want to run Quicken on your Mac, do not upgrade to Lion.