Strengths: Easy for baby to latch onto and doesn't create nipple confusion (my son switched easily between breast and bottle from 6 weeks)
Weaknesses: Can only fit 5 in the steriliser instead of the 6 normal bottles as the TT ones are wider necked. Sometimes need to put the end of a teaspoon thru the valve of a new teats to open it up so the air can get back in. Extra teats can be a little expensive.
Overall: Great, will be using them again with my next baby!