I see that Vodafone has VLAN tagging. Is this a good thing or a bad thing and why would I care?
You don't care if you use the supplied router.
You might care if you want to use your own router. Certain models don't support VLAN tagging (eg Apple Airport), but most do.
Great, that shouldn't be a problem for me then as I usually use the ISP supplied router.
I rang Vodafone to ask them to move me to fibre and they said they'd send me a new Ultra Hub router. I told them that they sent me one at the end of last year but they insisted that they send me a new one. Maybe the new one will be pre-set for fibre rather than VDSL? I dunno...
We had the same, and yes it was all set up to just plug and play. Didn't see I needed it but it but they insisted, and I was all for getting a new one that just worked without any fiddling around.
On the OP's question I don't see this as so much as ISP's reliability (they are all much of a muchness IME) but more a network provider one. Reliability is surely subject to the infrastructure in place that services a particular area. For example I have had no reliability concerns with VF, but a couple of neighbourhoods over they are always complaining about disconnections and downed service with VF. Perhaps asking your neighbours could give an insight as to reliability in your area?