Travel Cards and City Passes

I came across something called a "Go Pass" the other day.  It looks like you can buy a pass that will cover entry fees in to various attractions in a particular city and you effectively get up to 50% off the entry fees.  It looks like quite a good deal, particularly if you are planning to do a lot of touristy things.  However, sometimes these places claim to be reducing the price considerably but the discount isn't always what they claim.  I'm tempted to get one, but the downside is that you are then kind of committed to spending a day or 2 days seeing all those places, even if you don't feel like it when you get there!!

Has anyone used these?  If so, are they as good a deal as they appear?

I've also been looking at city transport day passes - these look like quite a good deal also.  In Chicago a 24 hour pass is only $10 for unlimited travel on buses and trains, which seems a pretty good deal.  We will be needing to get from the airport to downtown on our arrival, sightseeing and then from our hotel to the Harley dealer in Glenview (about 20 miles north of downtown) to pick up the bike to start our journey on the Mother Road - so $20-30 each for  3 days in Chicago seems like a good deal.  It looks like San Francisco does a similar kind of deal covering buses, trains and the tram cars.

If anyone has any good advice or knowledge of these things please let us know - all help/advice gratefully received!