I'm running Quicken 2005 Premier under Vista Ultimate RTM. I might be jumping the gun on this since Vista's not yet widely available. But, since Intuit released a "Using Quicken on Microsoft Windows Vista" Help Bulletin (just search for Vista in their Support area), I'd thought I'd pass on my experiences.
Firstly, in that bulletin, Intuit claims Quicken 2007 runs fine with their latest patches (R2 -- they probably wrote the bulleting before OR came out) under Vista. I have no knowledge of that version. However, they also claim Quicken 2005 and 2006 only have problems with accessing the Help files (scripting errors -- no fix) and with updating the Quicken version (need to run the manually downloaded patch as Administrator). With my Quicken 2005 Premier, which I manually updated from the initial install to OR while NOT an Administrator (without problem), my Help system seems to works fine. Where I do have a problem is with One-Step Updates (not program updates -- just downloading information from my financial institutions). One-Step Update works correctly. But, when I exit Quicken, it faults (usually -- I've had one or two cases where it didn't) and warns me that my transactions might not have been saved. AFAIK, all my transactions have always survived this. But, it's worrisome.
Secondly, I've got a problem with the scroll wheel on my Microsoft Wireless Laser Mouse 6000 (part of Microsoft's Laser Desktop 6000). Regardless of whether I scroll up or down in a register or anywhere else in Quicken, the window always scrolls up. I have to use the scroll bars on the side of the window to scroll down. Of course, this could be a problem with the mouse, the mouse software, or with Vista. But, since I see this behavior only in Quicken, I don't think so.
Other than that, Quicken 2005 seems to work fine under Vista Ultimate RTM. I just wish Intuit would acknowledge the issues I have (and which Vista has passed on to Microsoft and, I assume, Intuit). I worry about my data integrity because of those error messages. But, so far, things look fine.