While you might have wanted to wait until Three gets the rest of its 1800 spectrum from EE, I can't blame you for moving.
What's more, while I'd consider myself as most likely to go to EE if it wasn't for such a poor SIM only offering, I have been quite amazed at how good Vodafone now is around here and when I go into London.
Really, really good speeds (incredible in places when you've got 2600 available!) and the SIM only deal is good, especially now it offers you voice/texts in Europe and for data you pay £3 a day. As you say, it's £20 if you already had a Spotify sub.
As I posted a gazillion pages back, as time goes on, it's going to be harder and harder to slag off O2 and Vodafone for their lack of investment, poor speeds etc. O2 may not have the same ability to offer such high speeds, and might be a bit behind, but Vodafone has improved massively and it's only going to continue to get better.
I'm holding out, but my 4G speeds are terrible. I swear they're managing traffic heavily around here (Herts) and London, as I'm getting 1-4Mbps down (but 10+ up). 3G is usually much better, so it's not backhaul.
I'm also getting more and more situations reminding me of the bad old days of Orange, or O2 and Vodafone - where I've got full signal, but no data. Flight mode toggles may work, they may not. Sometimes a reboot seems to fix it, but ultimately it's not on that I can lose all data connectivity and be unable to find something on Google Maps when I'm standing on a street etc.