Well apart from not seeing them much, I suppose it's alright, you'll have a full time job paid every month, but depending on yourself that might not be enough!
If you think you(and they) can handle not seeing each other for up to 8 months wheb on deployments, and plenty of time inbetween that when you're away training etc then you'll be fine..
If you have young children you can very quickly become a stranger to them and you will likely miss key stages in their development. As wrecker has already said a lot depends on your partners ability to cope without your support. Missing out on family life was a key reason why I left the RN after 13 years service. There were other minor irritations but not knowing what was going on at home was the main one.
I've got an estimated start date of November time 2015 and by then my daughter will be just over one year old. I've spoken to a few mates currently serving and they're away from home a lot as was previously mentioned from deployment and training. I'm lucky my wife is very capable of essentialy being a single parent, however you'll have to work extra hard at a relationship with children as you will be missing out on quite large events in their life e.g. first time sitting up unsupported, first steps, first word etc. So when they're about 2-3 years old and have enough cognitive capability to recognise who Mummy and Daddy are when you're home you'll have to just be child-oriented to cement your relationship with him/her.
An example is my friend just came back from a 6-7 month deployment, and him and his wife bought a puppy before they left. He returned and the puppy had no idea who he was...sad times.
It is difficult to generalise as all relationships are different but my experience was that while I was away my family slipped into a routine of coping without me. When I finally breezed back into town although the welcome was warm the "Home is the hero safe from the sea party" was not always what I expected it to be.