The point of a water bottle is to hold water and not leak. Oh, and not contaminate your water, either. Since you have to carry it, a lightweight bottle that meets these requirements is better than a heavy bottle (like steel). Since you have to pay for it, a cheap bottle is better than an expensive one.

For all the reasons given above, a lot of people just carry a supermarket-variety plastic water, soda or gatorade bottle that they refill with water. They work, rarely leak, cost nearly nothing, weigh very little and are dirt simple to replace.

I use Platypus bottles myself because I can roll them up when they are empty and they don't take up space. They are also more durable than the cheapie plastic water bottles.