When Win7 came out, to much praise, I sat down at home and did some thorough tests. I am a developer who uses some resource-intensive applications for 3D visualization, physics simulations and graphic design. Currently my OS of choice is XP 64-bit.
When I compared the two however, while Win 7 stood out as being superficially faster through caching everything and *appearing* to boot your OS and your applications in a split second, prolonged use of these applications under this OS just ground to a snails pace over the course of a single weekend of use on a 16GB machine.
While WinXP64 didn't boot as fast or launch applications as quickly, it never crashed (Win7 crashed multiple times), performance within the applications I use was exponentially better when loading and managing large files, and the overall experience was much more robust.
Ultimately what it seemed to me was that Win7 was geared toward selling you a copy of itself in the store. 5 minutes of use will show you what appears to be an extremely fast OS that launches whole applications like they were text files. In reality it's Vista with an extremely efficient booting process and nothing more.
MS continues to push the bar though! XP used to be the worst OS you could make your machine suffer to run, but if history repeats I'm sure they'll release something so far worse in the future, after XP is deprecated and beyond maintaining, that will make me fall absolutely in *love* with the features of Win7.