I don't know about the IoW (and I gather its bus network is superior to many) but in general the pattern has been that rail services are withdrawn on the promise of alternative buses, then the bus service is gradually whittled down until it is virtually useless. Certainly that is what has happened over much of rural Britain (and France too I believe).
Yes I think that was discussed further back in this thread.
If it is proposed to close a railway and replace with a bus service, it may well be that the bus service will be cheaper, more frequent, have stops right in the town centres along the route, maybe have a more modern ambience, etc., etc.. But then when Mr (or Mrs) Private Bus Operator decides he's not making a sufficient profit, the bus service can disappear overnight and you're left with nothing.
But despite that pattern having been repeated over the decades, it doesn't stop numerous postings on this forum (not just this IoW thread) saying "line 'x' is an economic basket case, it needs to be closed and replaced by a bus", and getting quite forceful about it, as though they personally are losing a fortune.
I wouldn't like to guess why people love saying this so much - I assume it's not because they're desperate to save the pennies in tax said line costs them personally each year. Perhaps someone with a greater understanding of human behaviour can enlighten me.