I had swapped the rings on my Cannondale T800 from the stocvk 52/42/30 to what you are considering-48/39/24, on both my bike, and my wife's. The 48 rings I paid $10- each for-clearance at Nashbar (they were even Cannondale branded), and about the same for the other rings. Not pinned and ramped, but they still shift fine.
I have since switched the crankset to a "treking" crank from Nashbar for about $50-. It comes with a 48/38/28, and then I spent a couple dollars and put on a 22 inner. Not sure if I've ever used my lowest gear (22/32), but I like to know its there.
Its probably cheaper to get hold of a trekking crankset and new bottom bracket (if necessary), than it is to search out ramped and pinned rings to replace all three rings. *Shimano Deore cranset with 48/36/26 is currently $69.99 at Nashbar**
My wife is still using her pieced together 48/39/24, and has no problems with shifting, or anything else about it. We have never used chain watchers, but I have considered them on occasion.
We toured with the stock gearing for a couple of years, but felt that we would prefer to have some lower gears, and have not regretted it. Cannondale has since changed their cranks to a 48/38/28 for the touring bikes I believe. I find the 38 and 48 are a lot more usable when the bike is loaded. Maybe its just me, but the 52 big ring is pretty useless on a touring bike, unless its a big downhill.
This message was edited by biker_james on 10-25-06 @ 5:03 AM