We use the Tommee Tippee bottles to formula feed our now 3 month old baby. At three months we could move up to their level 2 nipples (medium flow) and/or we could wait a month and start him on the First Sips Cup.

http://www.toysrus.com/product/index.jsp?productId=3946484

Should we just be moving him up with the level 2 nipples and not worry about the sippy cup? The items are all interchangeable but I'm wondering if there is any issue with trying to transition him to a sippy cup style at 4 months rather than later. I think we're going to buy the level 2 nipples anyways but any thoughts?