Got my 200L yesterday. I will post a proper comparison and my feedback in a separate thread, but I just wanted to say WOW. This thing is just amazing. Even the packaging was so intimidating and with the hood it looks like an anti-tank missile launcher! That being said, my initial, extremely unscientific/rushed, test against the 70-200 IS II shows, as expected, the 200L being a lot sharper than the zoom. There is a massive difference that can easily be seen without going 100% crop when F2.0 is compared against F2.8 and if you were to go crop AND also go F2.8 vs F2.8, you see an even bigger difference.
The only downside I can say is the IS is a lot LOUDER with this lens than anything else I have ever seen. I know 5d3 has an issue with this particular lens, but mine, based on the date code, does not fall under that category (it's a 3 month old lens produced in March), so I know it's not that particular issue. I guess it's the nature of the beast.
The weight is a non issue with black rapid sport strap. I carried it around for 3 hours yesterday and felt completely fine.
Just waiting for my Don Zack cap to arrive at this point. Separate thread with details will follow, so stay tuned everyone!