I have been seeing more people with Windows Phone so it IS getting them more market share, but its a slow burn.
What Microsoft did is clear and Ballmer's vision although a big gamble might save them as the desktop OS continues to fade away.
They had 4 markets they wanted to target with 1 interface:
Desktop - The workers, people who still prefer to be on a big screen at home
Surface Tablets - People who don't want to carry around a laptop, but need something a little more powerful than a tablet. They should have not bothered with the Surface RT and focused on trying to get that Surface Pro cheaper.
Windows Phone - People who are tired of iOS and Android and want a simple phone
Gamers - XBOX One (This was their biggest failure so far because of their PR)
I think ultimately if things pan out well for Microsoft their market share percentages will look like this:
Desktop - Will continue to dominate, but shrink down to about 70% as Google and Valve enter the market
Tablets - I think the real Windows 8 tablets can get about 25% market share once the eco system is fleshed out
Windows Phone - 18%-20%
XBOX One - 40% if they can ever rebound from their PR disaster
People just like to use things that they are familiar with and Microsoft has a large enough reach that they can get their products out to many people. I hope they continue with that cheap Nokia Lumia line because it has sold big because of that $100 price tag...those are the commercials they should be promoting...not a terrible Surface vs Siri Ad that looks like it was done by some amateur YouTube user bored in the middle of the night.