I purchased 1 of these for my son as he preferred the 'big boy' potty over the little one. He absolutely loves it, you don't have to worry about it slipping, it's comfortable, and he doesn't mind being on it for a period of time. I bought a second for our other bathroom and for travel as it's totally worth the cost and comfort when it comes to potty training a toddler.
We do EC with our daughter, so even though she's only [age], she goes in the toilet. This seat is great because we're finally able to have her forward facing since the hole is small enough she won't fall in, and the guard still catches everything. It's very soft and doesn't leave marks on bums that sit there a while. Plus it's easy to clean. The suction cups don't seem to work on our wooden toilet seat well but it doesn't really slide around too much either, but we are placing her on it, she's not climbing on it herself, so it might wiggle too much then.