Adding to what denniskee and NorthernLights have mentioned, I've found that the 70-200mm range on a 1.6X crop camera, although still useful, is probably less so than if it were on a film camera or full-frame DSLR.
The 70mm end becomes 112mm, which is a little too long for general shooting. At the extreme end it reaches 320mm. Sounds good, but I still find it a little short for some events and also at the zoo. If you're dealing with domesticated animals such as dogs and cats, it's still useful, but it won't cut it if you're going to take a trip to Sungei Buloh for birding.
On the street, the telephoto end makes it quite apt at capturing those candid shots but its mere length and colour attracts enough attention to make you the center of attention.
Putting all of that aside though, the 70-200mm f/4 is a great buy for photographers on a budget. This and the kit lens will get you plenty of shots, with stunning sharpness and colour reproduction. And its light, easy to carry around all day even for a smaller-sized person like myself.
Also, look into Sigma's 70-300mm APO Macro...it gives you 100mm more at the tele end, but at f/5.6, you'd probably need to use a tripod. Observe your own habits to see if you typically shoot from a tripod or are mostly a handheld shooter. For slower subjects, IS might be more important to you than an extra stop.
