Yes, I think it's worth it. I go about once a month to keep in form for the dive trips I take each year (just got back from Red Sea). Good way to stay tuned up without hauling tanks, packing lots of gear, driving long distances, etc. I used to do that every week in the 22 years I've been diving and teaching but these days I just don't have the time (or maybe I'm just getting lazy).
We try and get a group together but generally it's just a few of us. The night dive is a nice feature and there are discounts on the weekdays and last dive on Sundays. They also have a decent full bar and restaurant. Sign up for the free membership and save a few euros off each dive.
I only live about 20 miles from Nemo so it is convienent for me to get there. If I were up in Holland or another long drive away...I'd have to rethink NEMO as a normal dive haunt.
Cheers,
DJ