[lowbone]

Sound to me like you are expecting allot from one lens. From walk around which usually includes some wide angle to events that would generally demand a telephoto. I think you should consider two lenses for your needs. For starters, the 70-200 f 2.8 is an excellent lens that will also work well with a 1.4 TC becoming a 280mm f4 lens. The problem here is that this lens as an only lens leaves you with a minimum of a 112mm lens when you take into account the 1.6 crop factor of your 30D camera. I would recommend against the 24-70 as well as the 50mm 1.2. The 24-70 f 2.8 still leaves you a little long at 38mm equivilent and the 50mm f 1.2 has not had the most sterling reviews especially at the fast stops. I think that considering your needs and your cameras 1.6 crop factor I would recommend going with a 17-55 f 2.8 lens. This is a terriffic lens, sharp even at f 2.8. I liked it so much that I sold my 17-40L.