I got a RF for DC1 due to the language thing but actually found it slightly annoying as, if she wasn't asleep, I felt obliged to be having pointless "conversations" with her to encourage language development when all I really wanted was some peace & quiet. Really, if you're doing the same 2 mile lap pretty much each day (as we tended to do due to it being the only route with pavements), there's not much to talk about by day three... "ooh, look, that sunflower is a mm taller than it was yesterday...ooh look, there's that dog again...ooh, look, there's the school you'll go to as a big girl" etc. So, for DC2, I decided that I was less bothered about it and, as the second pushchair we got was suitable from birth, decided I'd use that. But then I sort of missed him when I couldn't see him as those newborn gummy smiles are so cute and, with DC2, fairly easily obtained. It also means I can see if he's fallen asleep, been sick or is trying to do a poo, all of which are useful to know.
My conclusion is that I'm glad I've got the option but I don't think its essential.