I do have a "cake & eat it too" setup on my other bike: a triple with a mtn. cassette. It's awesome! Low gears to help you over some of the steepest climbs, or if you've been out in the East Bay heat for too long during a permanent route designed by one particular TEer who should remain nameless.

I have an SRAM 11-34 cassette (PG-970), Shimano rear derailleur (RD-760), SRAM 9 speed chain.

I could duplicate this setup on my other bike, but I'm considering other parts. Criteria includes even better shifting, durability, bling factor, budget.

Questions I've been mulling over include:
* I'm pretty sure I need a long cage derailleur due to the # of teeth on the chainrings and cassette. Could I get away with a medium cage derailleur?
* Top normal or low normal? I don't think low normal will work with STI shifters, but if it will, is there an advantage to using low normal?
* Should I use one of Shimano's shadow derailleurs? It sticks out less, which is definitely an advantage for a mountain bike, since it won't snag on the obstacles you tend to encounter off road. Is it an advantage for a road bike?
* Is XTR worth the price difference over XT, performance-wise? (It has weight savings, and gets points for the bling factor.)
* Does SRAM have any derailleurs that would work with my STI shifters? If so, does it work better than a comparable Shimano derailleur?
* Is it worth it to go with a higher end cassette to save a bit of weight? (Common sense says no. But I could be wrong...)

And yes, in case you're wondering, I do obsess over the darndest things.