Interesting if you've never read or seen anything about the Titanic, or if you're a completist; a waste of money otherwise.
I saw a very impressive Titanic exhibition about 10 years ago, with an amazing collection of artefacts and was excpecting something similar here. What little there was (the odd bag, a bit of crockery, luggage tag) was very nicely presented, so it all looked very impressive, well done on that front - but there just weren't many exhibits! Similiarly, the stories told about the passengers were very moving and interesting - but again, nothing you haven't heard before. Frankly, even watching the James Cameron film gives you more insight than this exhibition!
I didn't rush my visit, but read everything in detail, looked at all the artefacts - I was out after just 90 minutes! I went with my husband and parents-in-law - none of use thought it was worth the incredibly high entrance fee, even with the 2-for-1 offer we were lucky enough to have!