|I think you might be getting carried away with some sales hype. |
The base speed of 802.1.1 N is 100 Mbs. However it is possible to combine two channels to increase that to 100 Mbs. To get 300 Mbs you would have to combine three channels.
In any wireless network the actual speed you get is always going to be less than the stated maximum. So 150Mbs using two 100Mbs channels seems reasonable, perhaps even 50 Mbs using three channels. You are never going to see the theoretical maximum in less than perfect conditions.
It should be remembered that the 802.1.1 N standard is still in draft mode and has not yet been ratified. Until it is, probably later this year, the standard is likely to change.