When Masyn was a baby I tried it one day when she was 5 months old just because, and she loved it, it was a 2-handled cup she could hold herself and she took to it great. I ended up going cold turkey with Spencer too, the bottles we were using did not have a fast enough nipple for her, so at about 6 months I just gave her a sippy one morning with her formula in it. I do help her out with it a bit still, she needs to be reclined to drink it but can hold it herself (although I really think this is more of her wanting me with her than really needing help, and I like the snuggle!)
Heidi