I'm honestly having trouble rating this card.  I know that if I were to use it in limited in a red-white deck, it would be stellar, as it saves you from potential mana-screw situations.  But once I hit constructed and casual play, I'm stuck in the middle.  On one hand, Sunglasses of Urza can save you from mana-screw (just as in Limited), it can allow you to play cards with a lot of one color in the cost (stuff like Kiki-Jiki or Dawn Elemental), and you don't have to worry about being able to pay for anything.  On the other hand, is Sunglasses of Urza worth more than a well-constructed mana base?  I rarely have trouble getting the right color of mana over the course of several games, and this comes without Sunglasses of Urza eating up one to four slots in my deck.

 

In the end, I'm going to give this card a fairly low rating in constructed and casual, as it has limited use and I think that by making your deck correctly the first time, you don't really need to have Sunglasses of Urza.

 

Constructed Rating: 2.0

Casual Rating: 2.0