I actually care more about having competition and choices than just openness. Open source softwares suffer from stagnation just like the closed ones when they are left with no competition. Which is why I am actively rooting for Ubuntu Mobile and Firefox OS. I am also hoping with more Mobile OSes, we will start seeing standards to interact and share data between them.
You should also root for sailfish. That is one beautiful and open OS
Windows Phone is more open than iOS in the sense that you have multiple OEMs making multiple types of phones targeting different markets unlike the iPhone. For example, the Lumia 521 is just $130 off contract in the US. Also the walled garden prevents the malware problem that Android has. So it can be considered as a happy medium between iOS and Android.
The off contract 521 is awesome. I got a new one for $100 on ebay and it's specs are plenty for what I need. It rivals $500+ phones.
Yup, I managed to grab a new one at a Microsoft store for $86 (had a gift card and they had in store promos I abused). Most bang for the buck consumer product I have ever purchased.