The reason most of us are so excited about this is not necessarily because we hope to see a significant increase in the exchange rate or immediate general use but because a giant rich company like that actually announcing to the world that they think Bitcoin is a legit option is a huge nod of approval which will be heard loud and clear by everyone else on the sidelines indecisive perhaps about jumping in. In other words we are mostly excited for the PR effect this move will have that will eventually hopefully lead to more Bitcoin users and a higher exchange rate!
I hope that was clear enough.