Does the guy who is advising you to get rid of the Flight Deck ride a tandem? Maybe he doesn't realize how useful a gear indicator is in that situation. Also, if he only ever rides one bike, or several bikes that all have very similar gearing setups, then I can also see why he thinks it is easy to just know which gear combo you are in based on speed and perceived cadence. If you regularly ride different bikes with different gearing setups then a gear indicator is really handy, especially on the tandem where you cannot look down to see the cassette.
The Dura Ace inline gear indicators mentioned above are something that I've used a lot. Unfortunately, they don't work so well with the new generation of Shimano STI levers, which route the shift cables under the bar tape. With these, there is no ideal place to put the indicator like there was with the old routing. The best solution I found was by using Nokon housing, which allows very tight bends in the housing, and strapping the gear indicator to the side of the stem. However, the regular Nokon housing is too wide to work well with the indicator, I think the "slimline" version of the Nokon housing would have worked better, but that is even more expensive. Even so, I still found that I didn't like the gear indicator way out of my field of view down by the stem, and ended up rarely looking at it, so finally took it out.
Of course, if you want to upgrade to 10-speed and keep the flight deck in its current position, then you should still be able to obtain some of the previous generation Ultegra shifters, 6603. Alternatively, the new 10-speed Tiagra shifters, 4603, are virtually as good, and I believe they have an integrated gear indicator at th top of each lever.
Last edited by Chris_W; 04-06-12 at 11:33 PM.