Personally it reminds me a bit of WarZ, which is a really, really bad thing...
I also believe that if you have to add text to the items in an inventory you've done something terribly wrong. Item icons should speak for themselves and should only display text on mouse over or something similar. Text used like in your inventory mock-up is cluttering the interface and using more space than necessary.
In my opinion, the interface should be very minimalistic and kind of blur right into your surroundings (not necessarily talking about an actual blur effect here).
Yeah, you want your GUI to be as minimally intrusive as possible, Rust is more of an immersive sort of game, you want to feel like you are surviving, you don't want to feel like you are playing a video game, or at least that's how I feel about it.
Beat me to it, but exactly.