Pros: avoid restauraunt germs, portable, use at any height table
We got this in 2008 with our first baby. We haven't used it with our second baby yet because she isn't sitting up but the fact that we still have it (got rid of many baby items through several moves since we have such a gap between kids) shows that it was one of the products we loved.
I hated wiping down restaurant seats with alcohol wipes all the time. You never get it all and baby is bathed in alcohol smell. Our table was a different height from in-laws which was a different height from parent's. Ours was so high a traditional high chair didn't put baby at our level. This chair's portability saved us having to buy several high chairs and made sure she had one wherever we went.
I couldn't think of any cons. You have to clean it too, instead of the restaurant chair, but bottom surfaces are easier to clean later rather than having to clean baby surfaces before sitting down.