I'm in California and yes we are still doing Open Houses to give the property exposure. I think it is helpful if you are working with a few buyers, they can go out on the weekend easily and see a few things you have previewed for them.
As far as being effective they are for Agents with Buyers already, I'm not sure how many sales are actually happening with random buyers.
In my Central NJ market, BOHs are very popular to have and usually a great turnout will result if done properly. Up in my Central/Northern NJ market, they are popular as well but the turnouts are always dismal. In my Central NJ market, a good brokers open gets at least 10-20 agents; especially with the downturn of the ecomony and now agents LOVE free lunch. In my Central/Northern NJ market, I always go and see the turnout being 1, 2, 3 agents. A high turnout there seems to be 5-10, unless it is an extraordinary estate ($8M+); which at that point the turnout easy tops 100 attendees.
Hope this helps answer your question. Best of luck Janice!