Thats the only thing I worry about...is if my sellers check on me with that. Only reason I have not dropped it yet.
I wouldn't drop it. A real esate website without an MLS search feature is incomplete. The feature itself is advertising that you are a true professional.
And let's not forget that many sellers also become buyers and need to be able to search your website for a home. My sellers are always on my website searching the MLS to satisfy their curiosity about this or that.
If you're running 20-50 listings you can afford it no problem so I would just keep it so that your website remains a complete and professional presence on the Internet. When I see an agent website without IDX, I always consider them an amateur until further evidence proves otherwise. When I am looking for out of area agents to refer to, I always check their website and if it is not a good website with IDX and all the other things that look good and cost money, I move on. So it can also be a listing referral tool.
I'd keep it. Furthermore I'd make sure it was the best IDX available, something like Wolfnet with its map-based search that looks really cool and professional.