1) The rear derailleur pivots wear out and get sloppy after a season.
2) 1:1 ratio makes it take three or four strokes to shift down the whole range of gears.
3) With my giant hands I often shift accidentally.
I'm now running "vintage" Suntour Accu-shift Plus Expert thumb shift levers with an XT Shadow derailleur and XT 8 speed cassette on my trail bike (2x8 speed), and with an older XT derailleur on my commuter (1x8 speed). The shift action is the QUICKEST, most intuitive, simple, and concise of anything I've used in 20 years of trail riding. I never wanted 9-speed and would still use 7 if I could get good hubs. Shimano's new Shadow derailleurs are the best design and have the strongest spring of any I've seen.
Problems though are arranging the shifter around bulky hydraulic brake levers, and simultaneous control actions (shifting, braking, and holding on for dear life).
My trail bike with Suntour Accushift 7/8 speed levers.
Hey kids, gather 'round and listen to old-man Larry blather about bike shifting. Since 1988 I've tried most types of shifters for trail bikes. My first bikes had top-mounted lever shifters, or thumb shifters. Initially they weren't even indexed and you had to hunt around to get your derailleur aligned just right. Indexing was a glorious development.
Grip shift was short lived on my trail bike and has appeared on a cruiser or two. It is an elegant, simple, intuitive, light technology. I like it on a comfort bike or commuter, but on the trail the big wrist/arm motion is hard to isolate from your steering, and since my hands are freakishly large, I found myself accidentally shifting through tech sections. Not good.
Rapid-Fire and other triggers are really the most practical solution for trail riding. You can simultaneously maintain grip on the bars, apply the brakes, and shift. I do have some gripes though. Over time the action required to perform the task of shifting keeps increasing. I recall (correctly?) the original XT rapid-fire could down-shift the entire range with one thumb stroke but subsequent generations required two strokes. SRAM's 1:1 actuation on rear derailleurs increased a full range shift to three strokes. 1:1 is marketed as improvement to shifting accuracy, but I argue indexing and derailleur alignment are what affect shifting accuracy. Shimano accuracy was never a weakness. My other complaint with recent SRAM triggers is the hair-trigger and location of the up-shift lever makes it extremely easy to unintentionally upshift, especially with my goon-hands. I think Shimano rapid-rise shifters have the same issue, but I have never really used them.
My urban commuter. Note the contact between the shifter and brake handle.
Though I preferred Shimano shifters, I preferred SRAM rear derailleurs for their stronger springs. Unfortunately SRAM and Shimano shifters and derailleurs are not compatible, so for the last three seasons I rode SRAM. A downside to SRAM derailleurs has be the main pivots have shit bearings. I've been getting little more than one season out of SRAM derailleurs, while the same XT I rode for at least 3 seasons is still in service on my urban bike.
Shimano has finally issued the Shadow deraileurs, which besides having the strongest spring of any derailleur I've seen, also has a very practical low-profile design reducing the risk of bending your derailleur. The XT Shadow is the nicest I've ever used.
To me, more speeds are an unnecessary cross country and road racing trickle down. Racers like to meet an exact cadence so more gear ratios may make sense. The rest of us don't give a shit and just want our favorite few combinations as quickly as possible. More gears are pretty easy to ignore though and don't bug me as much as the wider cassettes that came with the jump to 8 speed. The wider cassette standard reduces how much width is between spoke spindles, which reduces lateral strength of the wheel.
Trail bike again. Note my 1.5 grip setup for those of us with less dainty hands.
Anyway, this rant is inspired by my latest shifting configuration. My increasing distaste for my SRAM set up has given me a new appreciation for a setup that can sweep the entire range of gears with one motion in either direction. I've installed a set of Suntour Accu-shift Expert 7/8 speed shifters mated to and XT Shadow derailleur and XT 8 speed cassette.