you have to remember that because of the smaller aps-sized sensor there is a 1.6x magnifier. your 28-135 lens will work as though it were a 45-216mm lens. With film cameras we usually referred to 50mm as line-of-sight meaning that it would look the same with a 50mm lens as it does looking directly at the object without a camera. So basically anything over 31.25mm with the aps-sized sensor will be zoom and anything under will be wide-angle. I fear that you will not have enough wide angle with the 28mm. This comes into effect when you want to get a large group of people or cars together or if you cannot back away further from the objects you're shooting. If I were to get an additional lens I'd look at one with extreme wide angle rather than getting that much zoom. Also you can usually forego the image stabilization with a wider angle and save some $. The wide lenses can be rather costly.

I'd think about the 10-22mm or 17-85mm ef-s lenses to get the most bang for your buck. in fact, a 17-85 and then a 75-300 will give you all you would need. if you can return or cancel the 28-135 you can put that towards the 70-300 IS lens because the long end of the zoom range is where you want the stabilization.

so many options! The magnifier causes a lot of confusion. I imagine in the next few years all DSLR cameras will use full size sensors to ease consumer confusion.