I want to jump in here. First of all, I'm not saying the rail link is the best thing since sliced bread. Nor am I saying it will fit all users needs. However, both Bangkok and BKK are better with it than without it. Don't you agree?
Have you ever been stuck in Bangkok traffic trying to get to the Tollway onramp? When traffic is at a standstill in Bangkok.... it can be ugly. I've left Suk 11 and it's taken me 1.5 hours to get to the onramp 1KM away. Of course I didn't know this when I hopped in the taxi, but it caused me to miss my flight. I've had similar problems in the morning leaving from Klong San or Sri Phaya. Note many of these locations are near a transit link. I'd gladly suffer with some luggage & heat issues if I could shave an hour off of my trip to the airport.
For all who work or commute regularly to the airport, Thais and foreigners, this will be a very popular choice; especially airport workers. To say this project is poorly constructed because it doesn't fit the occasional traveller who stays at 5 star hotels is a bit presumptuous. The same track also doubles as the local transit link along a very busy Rama IX route. Theoretically, with Thais taking the train, the Rama IX route may be less congested for those arriving from the airport. What if they'd built the transit link and DIDN'T extend to BKK? Wouldn't that be a crazier plan?
The fare is 15THB until 2011! Even when the fare goes up, it'll still be cheap to get to town, even for two people. Even if there is a taxi mafia or surcharge a Makkasan, it'll still be cheaper to take the train and taxi. No toll ways & cheaper per kilo rate for short distance trip. Makkassan is quite close to many of the tourist areas.
And I'll bet that the elevator/stairs/connection issues will be resolved. Thais don't like lugging baggage up/down stairs, etc. Because this problem affects Thais too, the motivation to build connecting walkways, down escalators may come faster than if it was only a foreign travelller issue.
Just a few ideas to think about and spur discussion. The rail link may not be for me or you, but I think it's a good thing in the long run.