Punki,
Only limitation is the city list itself. I think you can select all cities but your loading time may suffer.
Downsides are that it only covers major cities and the fares are not updated frequently. My guess is a few times a day. You have to select "book it" to list the lastest published fares. Lastly, you can choose only one fare; you can't not mix and match to fit your schedule. Looks like we have to wait little longer for this feature.
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Dan
"It is not doing the things we like to do, but liking the things we have to do, that makes life blessed." - Goethe