Dix 30 has no good restaurant but among them all, I guess La Tomate Blanche is the most decent. I come here every 6 weeks because I have work meetings but otherwise there are better alternatives in the area (outside of Dix 30).
The decor is nice, very classy. I came mostly for lunch time. They have a lunch "table d'hote" which is convenient but a bit pricey in my opinion. The service is slow at lunch and not that great for a restaurant that want to be high end.
Once I ordered the Tuna steak and specifically ask for it to be raw and they told me it's always raw and I still put emphasis on it again because I don't like to eat cooked tuna and it still came fully cooked!
If you have a car and have time, do yourself a favor and choose a better restaurant outside of Dix30.