I live on Peng Chau and my law partner lives on Ma Wan and the only time ferries have been canceled is during the typhoon (when most things were shut down). Very reliable, always on time, my ferry is pretty cheap, around 15 each way.
My ferry has an overnight ferry around 3AM, I think the last ferry before that is around 12:30 AM (I am not a late-night person).
Ma Wan/Park Island is connected by a bridge so can always get home by land 24/7 (taxi for really off hours but I think bu service all night).
I like Park Island, I think the development is very nice, prices are decent commute is decent (again, if you're in or near Central, I am in Sheung Wan for work). Some people think it is "soul-less" but I guess you could say all high-rises are like that.
I guess a lot depends on your schedule and how much partying/bar hopping whatever that you like to do...I have never been a night person so it doesn't impact me at all.
A lot of people say live really near work your first year at least and then decide if you want to move further away (islands/New Territories). But as someone else said, HK is pretty compact so you are almost never all that far from work. I am coming from the US where a 1 hour commute each way is about average (with the awful traffic involved in driving in most major cities). So my 30 minute or 40 minute ferry ride (two kinds on my island) doesn't really bother me- but it bothers a lot of people, only you know if it's for you.