Just a couple of tips: The free Gold games are always linked from the Xbox Live Gold slot that's always present on Home. And the rest of the sales, like back-compat, will always be linked from the Deals page, which can be reached from the Deals icon that's always right below the big banner section on the Store page.
And seriously, thanks for the feedback, guys. I work on the store team nowadays and it's really helpful. None of this is news -- we all use the store and want these features too! -- but it's great to hear your takes and your priorities here. LMN8R does a good job encapsulating some of the difficulties... A cart seems super-basic, but when you have stuff like the back-compat catalog it's a reasonably complex undertaking from a development standpoing. And filter-by-genre is one of my own number one asks.
Prioritization and timing has a zillion factors -- customer experience benefits, number of requests on the xbox.uservoice.com site, whether there's an overall OS update coming where it would make sense to launch a feature, time to develop, you name it. But trust me, the folks in charge want nothing more than for people to find shopping a pleasant experience. :) After all, something's gotta fund us making the next really cool, fun thing.
** As y'all know, I was on Qt3 for years before I was assimilated in Redmond, and I'm not here in any official capacity or representing anyone. But I really do find it super-valuable to hear what you guys think, and I appreciate the time spent on feedback. But this is just a guy asking his friends what they think... Thanks!