I should start by saying that my in-laws are great - I get on really well with them and would never want to offend them intentionally!
They very kindly bought us a highchair for DS when he was born - one of those Dr Evil style Bloom Fresco chairs they sell in John Lewis. It looks great but is horribly impractical and not overly comfortable for DS if his wriggling and complaining is anything to go by.
DH wouldn't let me buy an Ikea cheapie as he said his parents would be offended - fair enough I thought so we've made do.
However - SIL is pregnant and they've told us that they're going to buy the same chair for them since we "loved it so much" - I feel like I really ought to say something now so they don't waste their money when the IKEA one is so much better...but should I tell SIL and let her turn down the offer or be upfront with MIL?
DS uses the Ikea highchair at nursery and at my parents when we've visited and he sits perfectly still - I'm not sure if it's because of his big nappies but he never manages to sit straight upright in his highchair, always ending up at an uncomfortable angle or slipped down against the front bar.
I also think there are too many nooks and crannies for food to get stuck in!