Entry to the US from Dublin

Whats the procedure when flying from Dublin, is there a wait the far side at immigration or is it straight through when you have the valid papers, visa etc. Heard something recently about Shannon where there's no delays now, just straight through when you get there. Is there a difference between the two airports?

Depending on where you are flying to, there may be immigration clearance at Dublin / Shannon. All morning flights to the east coast that I have been on have immigration clearance in Dublin. Flights to San Francisco always have immigration in the US. They are in the process of extending customs clearance to Shannon and Dublin which means that you will be able to check baggage through and reach that utopian state of getting off the plane and not queueing....except for your baggage. ( this is an interim post awaiting the comprehensive explanation from EvilDoctorK !)

Going to New York, so can I take it there's no delay there except a baggage claim.

No guarantee that your flight will use immigration clearance in Dublin. Depends on the time of day and how busy they are but the vast majority of New York bound flights go through immigration clearance in Dublin. Leave plenty of time as there are a lot of flights that depart quite close to each other in the morning.

The customs preclearance in Dublin will be in Terminal 2 when they open it and if I could predict that I would be over on betfair !!

It depends on what time your flight to NYC is and what airline you are flying. Delta's NYC flight clears immigration in Dublin but only some Aer Lingus and some Continental Flights to New York do.