Negatives:
Constant erosion of your package.
Constant violation of your contract/seniority
Pollution
Traditional plusses like fairly quick upgrades and bases are now a thing of the past - therefore the sacrifices you make to come here are not worthwhile any more.
Positives:
Housing in HKG can potentially make you some cash.
If you get hired on a base it might still be a better option than your local regional scumbag outfit.