Hi, although I have no direct experience myself 4 of my mummy-buddies swore by them when first starting to get lo to drink from a cup, and tehy couldn't believe how simple it was. Having said that, when out and about they tend to use the valve type cups.
Like you I have collected pretty much every which cup going on the UK market, but with no joy, until we tried the Tommee Tippee cup. Its the one with two handles and a fold down spout, comes in red, blue or orange and is @ £2 in Tesco Superdrug etc. DD is now 19mo and still drinks from it!
HTH
H