I converted my Bridgestone MB-2 from six speed friction to seven speed indexed. The RD is a new Ultegra long cage and the rest of the drive train is XT. The shifters are rapid fire STI. The entire system performs flawlessly. The front shifter allows for trimming, so that's not a problem.

The cost is the only down side so far. It would have been worse if I hade gone with nine speed. There's less demand for seven speed parts, so you can generally get them much cheaper.

I've got a Peugeot PX-10 and a Gitane TdF that I haven't been riding at all. I'm sure I'll go back to them when the novelty of the index shifting wears off.