I got a 4d ultrasound with Charlie around 30 weeks, and I loved it. I took my mom and aunt who were visiting at the time, and they had never seen an ultrasound before so of course they were riveted. It was definitely worth it for me... we saw Charlie blinking, smiling, yawning... it was awesome!
With this second baby though, no 4d ultrasound.
Are you planning on getting a 4d ultrasound?