Not if the S line was also $300. Since the Nexus 5 is at a comparable price, I imagine a lot of people will gladly pay a little more to get a device that they can use well with one hand. I know I would.
If Samsung Galaxy S phones were the same price as their corresponding Note versions, we may see people choose the Note more simply because they believe they will get more bang for their buck.
That's not to say that people don't care about one-handed operation. There definitely are people who appreciate it, which is why devices like the Moto X are very popular.
In the case of the OnePlus One, the company has committed to a larger form factor for their launch product. I find it difficult to believe that they would bet their future on a large phone unless they believe it is something that would have the greatest appeal to their target audience.