[tqi]

It just seems like this would serve a very narrow market. When I lived in Lincoln Park, I usually planned on the trip to O'Hare taking ~90 minutes (Red->Blue). This was to avoid a $40-$50 cab fare. Would I have been willing to pay an extra $25 to shave off 30 minutes? Probably not.

If I was a business traveler, I would almost certainly prefer taking a car from wherever I was directly to the airport unless I happened to be staying/working right near the stop. The convenience of not having to get to the station, privacy, not having the transfer, etc would outweigh the 20-30 minute savings. Unless traffic was completely backed up in which case having that option is nice.