Is the 70-300mmL worth the extra dough over the standard 70-300mm? Thats the Question...
I tried the regular 70-300 in-store before settling on the L version eventually. I didn't evaluate its image quality but there is a HUGE difference between the 2 in build quality. You really do get what you pay for.
The regular 70-300 felt like a camera toy in my hand- the 70-300L feels like a serious piece of professional photographic equipment. Ultimately it's about the IQ for me and I've heard that the regular 70-300 is pretty weak at the 300mm end, so that's why I went for the L version.
Best thing is to try both out (if you can), then weigh the pros and cons of each. The regular one IS lighter, and 1/3 the price, so if weight and/or budget is an issue that's probably the way to go. But if you demand the highest in IQ it's probably worth it to save up.
...is the 70-200 II noticeably better than the 70-300L in image quality, and is the f2.8 worth the added bulk and weight.
depends on what you're shooting, and on what environment you will be shooting in. For me, the two lenses are interchangeable depending on what my telephoto needs are, exactly. Sports or indoors? f2.8 wins. Outdoors in daylight or animal photography? 70-300 with extra reach.
As for IQ, the 70-200 wins at the 70mm end, certainly. I'd even say the 70-200 at 70/2.8 outperforms the 70-300 at 70/4! At the 200mm end they seem to be quite close, though. I don't think you'd notice a difference in everyday shots...and in good light, the lighter weight of the 70-300 in that case is certainly appreciated. (Note that at 200mm the 70-300 has you at f5 minimum so it is nearly 2 stops slower here.)