Dublin is a hell of a lot more multicultural than it was 10 years ago.. There's a huge amount of Polish, Lithuanians, Latviand, Romanians, Nigerians..and Indians, though they're far from the biggest group. There are a good few people with the 'they tuk ar jarbs' attitide, but in general, Dublin is welcoming, although, when I visited London a few months ago, I noticed that London is a lot more integrated.
As for passports, you now need a passport travelling between the UK and Ireland, I'm not sure about the ferries because I haven't taken one in years.
As for working in Dublin, the economy is relatively strong, wages are high, there isn't a shortage of jobs if you have the qualifications. Inflation is pretty high at the moment, food prices are high, the sterling-euro conversion screws us all over even though the euro is gaining, and the housing market is a joke also, though it has gone down a bit in recent years.
Public transport- effective system still in progress..