You can ignore features like Launchpad if you don't want them; I do. You can also revert scrolling behaviour, disable word suggestions and autocorrect, disable "all my files", simply not enable social media integration. These aren't hidden preferences, they're just a second away in system preferences.

Meanwhile, by sticking to Snow Leopard, you miss out on:

* Robust full disk encryption (and the underlying filesystem improvements that allowed it to happen)

* Improved security (e.g. kernel ASLR, signed apps -- if you want them, sandboxing)

* Much improved user apps (Safari, Preview, QuickTime to name a few)

* Recovery partitions for improved disaster recovery

* Access to the App Store (edit: I'd forgotten you can get this on 10.6 too, though I couldn't speak to how many apps still support 10.6)

* For developers, there've been improvements to Objective-C, including the addition of ARC and simpler syntax

Snow Leopard is starting to look really old now, and as far as I can tell the only unavoidable difference is that Spaces acts differently. It's a big sacrifice to make just for that.