for those of you who own digital SLR's, i'm wondering if they are really worth it. i really envy the ability to use any lens, but i dont envy that you have to pay 150-500 dollars every time you want that lens. i know there are a lot of other advantages, such as better drives, faster shutter response, and usually higher resolution, but i can survive without those advantages. tell me from your experiences is full control over the lens really worth the extra dough?