Apple want you to use the App Store since you have no DVD drive. They also want you to buy iWork so MS office - the worlds most popular office suite - is not on the app store. However, in Iworks defence, you can buy individual apps so if you dont use their powerpoint just buy word and excel.
Before you buy MS office though, download and try Open Office. Its free and almost as good (just not as pretty, but hey its free!).
As far as I am aware Microsoft have not submitted office to the app store. Your post implies that Microsoft has and that Apple rejected it. Apple can not put office on the app store without Microsoft's approval. I'm positive that apple would love to take the 30% they would take from Microsoft if office were on the App Store.
http://www.microsoft.com/mac/buy
Choose BUY on whichever version you want.
You can then download it from Microsoft.