EF 100-400mm f/4.5-5.6L IS USM Good for general use?

I want to do some indoor with low light and flash and a lot of landscapes, sports, and people outside.

Would this be a good lens for all those?

no. the 100-400 is fantastic for outdoor use but:

1) it might be too long for landscape (i used it before for seperating the subject but normally, landscape can really benefit from a wide angle)

2) it is too slow for sports unless the weather is perfect with nice light

3) the flash is useless on such focal length unless you use an extender of some sort and trust me, you do not want to use this setup indoors or on some one's face.

the bottom line is even though this lens has a very versatile zoom range, it is really not suited for all kinds of photography. for indoors, nothing can beat fast lenses with 2.8 or faster.

so then this would be a better lens for me maybe with a 2X extender?

EF 70-200mm f/2.8L IS USM

that would be a much better lens because you can use it for indoors, portraits, sports, wildlife and pretty much everything else you can think of. however, i would advice against the 2x extender and go with the 1.4 instead. the 2x extenders really degrade quality unless you are using one of the big guns (300 2.8, 400 2.8, 500f4 etc..). with the 1.4, you should have fantastic quality and close to 300mm at f4 which is still plenty fast..

I had the 100-400L and its a nice lens for outside,70-200f2.8L and 2X don,t even come close,70-200f2.8L with 1.4X is a superb combo.

Sweet. I think that's my first lens then. (besides my kits 18-55)

So if I get the EF 70-200mm f/2.8L IS USM Then really I wont need any other lenses that hit inbetween 70 and 200mm right?

I have both, and they're complementary. i wouldn't dream of trying to use the 100-400 indoors, especially at the long end, but it'll blow away the 70-200 +2xTC outdoors. It's too long for most of what people generally want for landscapes though, especially with an APS-C sensor.

Photolistic wrote in post #2035757
So if I get the EF 70-200mm f/2.8L IS USM Then really I wont need any other lenses that hit inbetween 70 and 200mm right?

probably not. like we all said, the 70-200 2.8 is fantastic and it is a great buy. also, like Jon said, the 70-200 and 100-400 are really not competing lenses, having both is a very good idea. however, for your needs, the 70-200 should come first.

Photolistic wrote in post #2035617
I want to do some indoor with low light and flash and a lot of landscapes, sports, and people outside.

Would this be a good lens for all those?

Not at all...

70-200L 2.8 for low-light indoor and flash, sports and portraits (if you really want TC) ...not at all for landscapes. You would need a lower range TC for that. (ie: 10-22, etc)

Not a good indoor lens, this bad boy needs light to work properly, lots of light