What I like about it is that I am able to choose to go to the website, knowing that I will get to see an extra page – but if I don't, no worries, since it will be updated on tapastic eventually. That is how I read Shadowbinders for example. Their website is often a little further ahead, but their tapastic account will be updated a little later.
I was speaking in very loose terms. Of course important material that enriches a readers experience should not be held back from the general public.
The quality - hopefully - is the biggest incentive for most supporters. However, perks like receiving sketches or unlocking episodes early for supporters are definitely tools meant to draw in more "paying customers". (Even if the comic creator does not plan on using those perks for that reason.)
Of course this does not work for everybody - for me it obviously has the opposite effect, and for you it does not matter since you are choosing to support for different reasons. But if there are people like us who don't care about early episodes, there must be people who love it and decide that this is the reason why they will start supporting a certain comic.
That is also the reason why I would not unsubscribe to a comic that uses the unlock feature. Every comic creator has the right to use everything he has available to draw in more supporters. But it does not change that it annoys me.
In the end it boils down to the changes that Tapastic has been talking about. If their updated notification system takes care of messages meant only for supporters, then I can't wait for it to be here.
Until then some people will continue to be annoyed by it and some others might choose to subscribe because of it.