To be honest, I still feel weird to see blocktrades doing this. I think mainly because you have such a strong brand image of quick and no-fuss exchange but buying SP delegation is totally another thing. Wouldn't this undermine your brand somehow? especially to those outside the Steem community... I am not sure, maybe you have evaluated this already.
One particular good thing from this service though, in addition to MB's similar service that is, is that this will facilitate those who want to give power to some Steemians but do not want to reveal their Steem identity or even do no have one at all!! So this is somewhere you might consider focusing for your future marketing direction. Say if Vitalik Buterin sees a Steemit post about him and likes it so he decides to give the author a gift in this way but he doesn't want to register at all (yeah, I can imagine that...). This is what he can use. XD
The purchase process for Steem Delegations is actually pretty much the same as normal purchases of coins (except that we will offer the option of delegation renewals in the near future). So I don't anticipate it will cause any confusion to our existing user base (and so far, we haven't seen any).
Naturally, there will be some people who will think it's a bad thing: this is true of just about any new thing in crypto from what I've seen. As one of the largest steem holders, I did give it a lot of thought before deciding to offer the service, and I'm sure it will be a net positive for the long-term value of the coin.