We swallerd a monstrous-for-us bitter pill when we crossed over to the dark side and started offering these. It went down easier because, in the big pitcher, does it really matter what kind of mechanism you use to shift? Barely. These make a simple process even simpler, and they make riding a bike less stressful for some, so we are all, officially, for 'em.
Trigger shifters are ugly and take up a lot of room on handlebars, but they're good for people with small hands or if you're building a bike for someone who can't stand to mess a shift up now and then, which, with friction shifting is bound to happen on bumpy trails occasionally.
We're selling them for rear derailleurs, because front indexing is the worst. Use a Silver or SunRace lefty for the front.
Initially, click the shifter so that your chain is on the smallest cog in the back. Then spin the pedals and click the shifter once. If chain doesn't jump up to the next cog, your tension is too loose.
Secondarily, if it jumps past the next cog, your tension is too tight. Work your way up the cassette using this method until it works for every shift.
Tertiarically, make sure your derailleur hanger is straight.
Quadrophonically, if you're putting these on upright bars, look at the Billie, Tosco, Bosco, Losco, and Choco BEFORE considering the Albatross. The Albatross is groovy but has a shorter grip area, and these take up more space. You'll still have 100 percent grip space for one hand on the Albatross, but on the others, with longer straight sections, you can probably find a second, forward-of-the-brake lever grip, too. Small point. Ignore this.
Derailleur cable included and installed.
Sora R3000 (9s)
Acera M3000 (9s)
Altus M2010 (9s)
Claris R2000 (8s)
discontinued by Shimano, sorry - Deore M590 ISLM590RA, Alivio M4000 ESLM4000RA