It's hard to believe that someone would find Ulusaba to be a "huge disappointment," as described by a previous reviewer. I suppose it depends on one's expectations. If you expected your young son would be allowed on safari drives and he wasn't, you would be disappointed. However, you need to do your homework. "Not worth the money?" Again, personal opinion, I suppose.
My wife and I stayed at Ulusaba Safari Lodge in early March. It was fantastic. The accommodations, public spaces, service, and safari drives were all outstanding. It wasn't very busy so they upgraded our room. River Lodge 1 had a large bedroom, bathroom, and deck overlooking the dry river bed. I could envision rooms that were more deluxe (plunge pool, better view, bigger, etc.) but it would have been overkill, as we were in our room for about 20 minutes per day while not sleeping.
Safari drives were great. We saw the big five (and more) up close. Couldn't have asked for more.
I could go on and on but I'd simply repeat all of the positive feedback elsewhere.
If I had to find flaw, I would say the food was only good, not great. If you're a foodie and want your salmon tataki with only a razor-thin sear, you'll likely be disappointed at times. However, simple dishes were prepared skillfully and ingredients were always fresh.
Also, we drove ourselves to Ulusaba from Nelspruit airport via Hazyview. It's a rather easy, safe drive but you need to allow 3+ hours to get back to the airport. We scrambled a bit to make our flight back to Capetown.