Hellobee Boards

We really like the Thermos Foogo and Funtainers. They keep everything really cold and are very easy to clean. And very easy to suck the straw.
BUT as he's gotten older I tend to only use them when I'm closely supervising. They do spill easily and as he's gotten older he thinks it's neat/funny. When he was younger (6-13 months I'd say) it was a non issue.

Also we used life factory bottles as an infant but they were too heavy for her to use herself as a sippy.

@Mrs. Goose: yes! We have hardwood floors and LO is a thrower. Other than being worried she might concuss one of the dogs it's stood the test of time. Not leak proof to toss in a bag and bring somewhere but doesn't usually leak if tipped over or thrown. We also have the foogo thermos stainless steel and it leaks like crazy unless always upright. I gave it to her in the car once and will never make that mistake again! Had to pull over to retreive it. Does work great to keep milk cold for long trips though for supervised drinking.

ETA: LO is 17.5 mo so we've been using the green sprouts cup for almost a year now!

We use one Foogo and several Funtainers, rarely do we have issues with them leaking. We only serve water in them and don't wash them as often as we probably should (we only hand wash them). We try to avoid plastic too. We served our babies water in a stainless steel cup with a stainless steel straw. The cups were pricey, around $30 or so for 4 of them on amazon but we use them all the time now 4 years later. The straws were cheap, also on amazon. We still serve our 2 and 4 year old milk and smoothies in their open cup with a straw in it. We have spills but in general they are pretty good and its nice to toss both pieces in the dishwasher (the straws sit at an angle in the silverware basket so they don't fall through the grid) and not worry about nooks and crannies getting clean!

As for teaching baby to drink from a straw, we placed the straw in a glass of water, then covered it with our finger and held the end in their mouth. As soon as you can feel them sucking, let go so they get a little water. We've also let our kids drink straight from an open cup if they want to, of course we get lots of spills when they are first learning but we put very little in the cup.

@Mrs. Goose: mine honestly do not leak and my son THROWS it and holds it upside down all the time.
If people experience leaking it's because they aren't putting the silicone straw in properly. There is a little "valve" that you have to be sure is covered by this piece of silicone. My nanny and husband sometimes don't check this when they put it together out of the dishwasher and THAT is when it leaks. So I would bet a ton of money that it's user error, not the cup itself. If you do it right, it's the best of 6-7 cups I've tried.

ETA: I guess I can only say this about the plastic cup though. Maybe the stainless one does have an actual design flaw. I'm going to get it to test it out