I stayed at the Namba Oriental for 5 nights in September 2010. The accommodation was excellent. Very clean rooms and bathroom, excellent television reception, internet connection for the laptop etc. The elevators were fast and there was never a long wait. The hotel is in excellent condition throughout.
My only gripe was the breakfast. The dining room seemed to be constantly full to overflowing. I tolerated that as I thought the breakfast was part of the room rate. Shock horror....upon departure I was presented with a bill for nearly 1500 Japanese Yen per breakfast consumed. MCDonalds (located next to the hotel) did a comprehensive breakfast combo for around 500 yen and it was a more appealing option. Breakfast aside, this is a very good hotel.

This hotel was decent. It was close to Dotonbori which was great! The room was a little old but nice. My chief complaint is that the whole place smelled like smoke. I wanted to hold my breath in the lobby, elevator, and hallways because the smell was so strong. If this doesn't bother you then the place was nice. Fortunately we were in a nonsmoking room so it didn't smell like the rest of the hotel.

Decent room, fun location in the middle of all the action and amazing staff who couldn't do more for us. You're right by several subways and 100's of restaurants and bars. Only drawback is we didn't get great restaurant recommendations so prepare before you go.

A decent place in every respect, the basic twin room we stayed in was small and not cheap.
I think you are paying for the superb location near to the Nankai Namba station in the atmospheric pedestrianised part of town.
Room although small was well laid out and spotlessly clean.
I cannot but think though that there is something else out there that just does things that bit better for around the same price - thus only an average rating.