The glass boxes can be used to freeze, cook in the oven or heat in the microwave. There is, in my opinion, one downside. The boxes don't close watertight, so it is hard to take them with you when there are liquids inside. I can work my way around this.
Apart from that I have nothing but positive experiences. I dropped one of the boxes on the tiled floor and it didn't break, so very decent quality product.