I'm living in the Harbourside at the moment. The gym opens at 7am, so you can't use it in the morning if you start early (I start early too so this is annoying). It does stay open until 11pm though. The pool opens tomorrow (1st April) so I'll let you know what that is like.
Getting a taxi back from Central/LKF/Wan Chai costs about 100-120 HKD if you take the Sheung Wan tunnel and 80-100 HKD if you take the Causeway Bay one. Either option is 10-20 minutes depending on traffic.
There are not so many places to hang around here - Stormies Bar seems to be the only choice - but honestly Lan Kwai Fong and Mid-Levels are 15-20 minutes away by train or taxi so who cares?
If you work in ICC then you can nip home in 5 minutes, take a shower, get changed and head out to meet your friends on the Island for the evenings. Seems like a great option to me! I work in Central and it takes 15 minutes door-to-door to my office by MTR (7.8 HKD) or taxi (100 HKD).