I am an estate agent in HK and an expat. I can say with some certainty that Bella Vista is one of the best values in MidLevels because it is very popular among young single professionals. It has killer views (esp above 17th floor or so) and is one of the select buildings in MidLevels with its own pool and clubhouse.
Rents in general are up in Hong Kong this 08 Spring and Summer because sales are flattening and that's how it works.
If you want an expat agent priv message me, or I can refer you to someone.
I know for a fact you can get in the 20'sK per month for a flat in BV that is in the 600sf range. Always price it high, BV is popular and there are some landlords who price low and others with similar flats who price in the high 20's. The customer can bargain you down if you're too high, or your landlord side agent can advise you.