Re: 3D/4D Ultra sounds....
I had one done at 26 weeks. I loved it. We wanted to be sure she was a girl so we had it done by a place you pay for but done by a trained US tech that had previously worked in a hospital. It was about 20 min and AMAZING. It was around $200, but still less than we just paid to have a 2-d one for a due date done at our clinic (it was $287 and we don't have maternity insurance) So I don't feel it was overpriced at all compared to the doctors clinic.
Most of the tv programs and articles I have read against private US are because it is replacing people seeing their doctor for the diagnostic ultrasound. Most of the people doing these are not trained in diagnosing anything they see other than gender.
Also if they do a prolonged US for over 30 min or something. Just make sure the people are trained and I think you are just as fine as with hospital to do it once. I had to have a signed note from my doctor and she thought it was fine (although I don't always blindly agree with all doctors).
Post your pics if you decide to do it!
Mama to 3 girls!