The Sheraton on the Park is in a midtown location across the road from Hyde Park and the park view rooms look over the park, cathedral, and across the eastern suburbs out to the ocean. It's a terrific hotel, the rooms and bathrooms are tip top and because it isn't at Circular Quay, it's usually good value. I usually book via lastminute.com.au or wotif.com.au.
If you need apartment style accommodation, Mantra is reliable and keenly priced with several properties around the Sydney CBD. You won't get much in the way of views though.
All under AUD$300 per night