If you don’t believe that drivers make a difference in terms of performance and stability, here’s a real-world example.
I recently installed Windows 7 beta on a Dell Studio Hybrid. This system is actually a notebook PC’s guts crammed into a tiny desktop-sized box with no expansion slots, so it should be no surprise that its integrated Intel X3100 video circuitry identifies itself as a Mobile Intel 965 Express in Device Manager.
The Windows 7 beta initially installed an Intel driver from its default collection, dated October 2008. Here’s the Windows Experience index as it appeared after completing the initial install:
Windows Update kindly offered me a new driver, this one dated December 2008. After installing it, the Windows Experience Index display nogted that it needed to be refreshed. After I did so, here’s the number that appeared:
Now, 3.1 to 3.5 doesn’t seem like such a big jump. But take a closer look at the individual measurements. The 3D performance benchmark went from a mediocre 3.1 to an impressive 4.9, just on the basis of a single driver update. And the difference is noticeable in everyday operation.
I’m especially impressed to see this sort of development effort being turned out by hardware manufacturers while the OS is still in beta. A big difference from the days when Vista was under development.
Ed Bott (@ wordpress.com) 
I wonder if HW manufacturers recognize the role they played in the negative reaction Vista inspired, or if Microsoft found the carrot/stick they lacked then.
Drivers make a huge difference, especially the Display card ones. I for some reason feel that nVidia under tweaks its cards. Its always certain driver updates from them that suddenly the card gives a higher FPS/WEI.
My SoundMAX intergrated sound wasn’t working on my computer with Windows 7 beta. (This is my backup/old PC, the motherboard is an Intel D865GRH). I had tried installing the latest drivers from Intel’s site I could find, but to no avail. I did Windows Update yesterday, and it pushed an update which fixed it. Pretty awesome
Ed
That’s a good outcome and bodes well for the RTM of Windows 7.
The biggest issue to overcome for any major new Windows release (i.e. Vista) is the drivers. System instability and slowness occur when the drivers suck, and other problems compound. Bad drivers are probably the single biggest reason why Vista had launch problems.
It is typical for a dot-release to have fewer hardware problems than a major release. How many problems did XP SP2 have? (SP2 was about as big a change to XP as 7 is to Vista. And just like 7, the driver model didn’t change.)
The real test isn’t Windows 7. It’s Windows 8.
Ed, as a side note, I recently upgraded to the newest ATI video drivers and found they had advanced controls for changing the card’s GPU and memory speeds. Setting those to the minimum possible levels seems to have solved my video crash issues. Definitely cheaper than a new power supply!