I bought one of these for my daughter and think it's fantastic, they're not cheap but they will still be useful in years to come.
Whilst she was a baby we had the guard bit round the front and used the harness for a while, both of which you need to buy the baby set for (optional extra), and now she's a toddler we've taken the front off and she climbs up herself and sits down at the table. It can be adjusted to any height of table so she has her own chair without the need for a booster seat, and I imagine she'll still be using it right up until she is the right height for a normal chair.
The only downside is that she does like to kick off from the table if she's in a funny mood, so if you can have the back of the chair very close to a wall then that will avoid a fall backwards from quite a height.
I have recently bought another for my son.