Up until last year we've always until Orlando Int and were pretty apprehensive about having to use Sanford twice last year (we changed to using TCD for our package) because of the longer drive and it being a smaller airport. However, we couldn't have been happier!
Sanford is much smaller and (unless you're unlucky enough to land with another couple of planes) much faster to get through than OIA. Both times we went (in the middle of Summer) we breezed through immigration and baggage in under an hour. The first time we were in and out of the airport in half an hour!
The drive from Sanford to the Disney area is longer than from OIA but not hard at all. It was my boyfriend's first time driving in the USA (and indeed on the right-hand side of the road) and the drive helped him adjust perfectly. We took the toll road- one straight road, which is usually quite quiet and helped him build up his confidence. The tolls come to under $10 from Sanford to Disney and you can get change at the booths. We got to our villa at Champion's Gate in about 45mins.
The only suggestion I would make is to try and book the Sanford Guest House for the way back to the UK. We found this a great place to relax before the flight- especially since we were delayed 3 hours (due to last Summer's security issues) and the general departure lounge got REALLY busy (there was no seating space left on the floor!).