As I live close to the course, I can't comment on the accommodation. At the risk of offending anyone who lives there, there's bugger all to do in Dundrod. I'd go with some digs or similar in Belfast (especially if you've not been over before), which will give you plenty of options.
The event (well, Saturday anyway) was rained off last year, which is a chance that you take with these things (staying in Belfast would that mitigate the problems if that happens again).
Event wise, I think that it's the best biking event going. A magical track, riders going hammer and tongs with no time-trial to consider; a 130+mph average

; all the top road racing names; I'm a huge fan!
I live 5 miles from the track, you're welcome to a coffee/beer if you're in the vicinity. (I had a BBQ on the same day last year - the wettest day for 70 years or something...)
Patrick.