[obsoquasi]

It was suggested, that you buy the 55-250mm. Don't do that, this lens isn't worth the plastic it is made out of. Okay, maybe that was a little to harsh a judgement - it's not a REALLY bad lens. But once you have tried the 70-200mm F/4, you will ask yourself, why you didn't buy that in the first place. Personally I'd go for a 17-55mm and the 70-200mm F/4. I have a feeling that we will see some improvements in the ultra-wide to wide-angle segment, that will be compatible to FF. I personally use a EF-S 10-22mm (which I find great, if maybe slightly unsharp), an EF 24-70mm F/2.8 wich (on a APS-C) is "okay" for portraiture on APS-C, but really has an odd range there (38-112mm), and two 70-200mm IS (F/4 and F/2.8) which I love both, but would probably stick to the F/4 if pressed, because F/2.8 isn't really that much different. That's to say, if with F/4 you didn't get enough light, chances are, F/2.8 won't be enough either. But the F/4 is sooo much lighter!