I've had my band since they launched and it's great on the buses and tubes. It's just as quick as using an Oyster and it saves time fishing an Oyster out of my wallet. It's also been useful for the odd sandwich or coffee. The cards were always designed to expire at end of May, so it's not exactly being switched off. An email from them last week said they were introducing a new slimmer version of the band and gave me the opportunity to pre-order the colour I wanted.
Meanwhile once the card expires in a few weeks, I'll just use my Barclaycard Paytag card in the band instead and will use that until the newer version is released. You really can't beat the band for convenience.