The traffic on I-4 can be slow to stop and go heavy in places. But still probably faster than the surface roads. I would guess 20-40 minutes, depending on where you are staying and the traffic. The convention center is pretty easy to get to off of 528.
Spend some time with google maps to get a sense of the traffic and the route.
So yes, a bit of a pain, but offset by being in the Disney bubble at the end of the day.
Will you have tickets or an AP to get some park time while you are there?