The proposed cap would be at the top end of the range recommended by the independent immigration advisory committee last week - probably a consequence of the Tories' need to cut a compromise deal with the Lib Dems (who have a much less stringent policy on the issue). But there are some important exceptions: notably, that companies will be allowed to transfer as many staff as they like from other countries as long as they're earning over 40k (a decent indicator of their skill level). Business groups argue that this is good news for UK plc, since multinationals will be more likely to invest here if they're free to bring their own senior managers across.
Importantly, it sounds like there will also be some kind of exemption for scientists, to protect Britain's research base. That also seems sensible - but since there are likely to be other exemptions too, and since the rule legally can't apply to EU migrants (a point Nick Clegg made forcefully before the election), the Coalition will inevitably stand accused of coming up with a cap that fails to do what it says on the tin. The other potential problem is the likely crack-down on student visas; it's right to stop those FE colleges peddling dodgy non-degree English courses, but you don't want to discourage the best and the brightest kids around the world from coming here to study.
Still, since the election suggested that majority opinion favoured tighter immigration controls, the Government has to be seen to be doing something. And hopefully this approach will allow it to bring down overall numbers without affecting UK firms' ability to hire highly-skilled people. Though of course this does point to a bigger problem - why is our education and training system not producing the kind of skilled talent we need? It'll take much more than a bit of behind-the-scenes political deal-making to solve that thorny problem.