It has to be better than just hanging out in full open exposure.
It would basically be the same deal as a tent minus the setup work. You'd still need a means to keep yourself warm, furs, blankets, or endure elements would be in order.
That's much how I viewed it, I think of it as the magic version of very high end modern tents (or better ancient onces made by peoples who had the right materials and knowledge).
It seems effectively wind and waterproof, so as a GM I'd never have those being factored in (non-magically), and I'd give it some consideration, in addition to the things LazarX already mentioned, in how warm a PC is.Plus, of course, it's obvous bugless benefits in warmer lands.