I only have one bike (of 13) that has indexed shifting and that is my hardtail mountain bike... it can actually use this to it's full potential and mountain bikes are what indexed systems were originally designed for.

I was weaned on friction systems and once you learn how to shift properly there is nothing better although it seems many folks have lost or never gained the ability to use a non indexed shifter system.

Once you fingers develop the memory of where the shift points are you also have to be able to soft pedal during shifts to make the transitions as smooth as butter and this carries over to using indexed systems as well.

It's like the difference between driving a car with an automatic to one with a standard tranny and a clutch.

A good friction system will also be more reliable, long lasting, and require far less upkeep and tuning than an indexed one.

Suntour probably made some of the best non indexed shifters ever and a conversion the other way does not have to cost and arm and a leg... the shifter has to match the freewheel / cassette you are using and the derailer should not matter.

You cannot mix Suntour indexed shifters with Shimano drives (very well) since the cassette spacings are slightly different between them.

Ai also prefer friction controlled front derailers over indexed as they work far better this way.