The best advice I can give you coming from someone who did the same search last year is to check craigslist and newspaper classifieds constantly, and drive around. I know it is super time consuming and tedious to drive around, but that is the best way to find out about good apartments in the downtown area. Because the nice ones are in demand, many landlords don't have to do a lot of advertising, so a sign in the yard/window is all they need to get a renter within a very short time frame. I found my apartment by seeing the "For Rent" sign outside.
Driving around just this morning I saw a sign outside Boylan Apartments that said they are now renting. Check out
Downtown Living :: Downtown Raleigh, NC where you can find the contact info for a lot of the professionally managed downtown properties, so you can try just calling instead of driving around for some of them. Condo rentals will most likely not be handled by the condo management since they are privately owned, so those you'll have to find through classifieds.
Best of luck, I know it's an arduous search!