Casa Del Mar was my first experience in the DR and we went in March of 2000. The place was clean and huge with an excellent beach and pool area. If you like to snorkel, I'd recommend bringing your own gear because of time/rental limits the resort puts on their gear..usually only an hour a day. We were in the water constantly because there was so much to see.
We did take the full day tour into Santo Domingo and enjoyed it, so if you don't mind a long bus ride, it's worth the time IMO.
I still have pictures up of Casa Del Mar, snorkeling and Santo Domingo on my website if you're interested in looking before you go.
http://www.geocities.com/tanabtvs/caribegallery.html