We’ll update this as we come across perspectives that add to the mix:

John Shinal, MKTW: “The beginning of the end for Semel came last summer, when he announced that Yahoo would delay the implementation of new technology that he had promised would boost profit margins on search into the same league as Google’s. Between then and last week, when many shareholders voiced their anger over Semel’s pay package, the calls for his ouster rose to a fever pitch. On Monday, the Yahoo board finally heard it. They decided that to compete with a rival run by two Stanford computer geeks, Yahoo needed to put its own Stanford computer geek in charge.”

Larry Dignan, Between The Lines: “As far as perception goes Yang is missing a key component of the founder-returning-to-save-a-company tale – he never left. Yang has been involved with Yahoo management and worked closely with Semel. Couple that fact with this one–Yang was never CEO in the first place as Tim Koogle and then Semel ran Yahoo–and you have a conundrum. ... Yang will have a difficult time initially because an outsider would at least enjoy a honeymoon.”

Charles Cooper, CNET News.com: “as much as the financial mandarins hated Semel, Wall Street may well rue the day Yahoo put Jerry Yang back in charge ... Not that Yang’s a bad guy. To be sure, he has a blind spot when it comes to Internet freedom and China. Then again, so do a lot of his brethren in the technology industry. The problem for Yahoo is that Yang’s about as exciting as melting vanilla ice cream on a hot summer’s day. Droning on about the management changes at Yahoo during a teleconference Monday, Yang sounded like a male version of the Stepford Wives.”

Kara Swisher, AllThingsD.com: “This move, as with all things Yahoo of late, is typical–a lot of very dramatic things happen all the time, but nothing actually seems to change dramatically. ... to hang all the problems on Semel, which is clearly being done here, is both unfair and untoward. He clearly did not perform in the past three years, fighting an onslaught from Google that was almost impossible given both his and Yahoo’s lesser technical proficiency by comparison. Neither Semel nor Yahoo has been nimble or nerdy enough to pull it off, although that perhaps is no surprise. ... after this move–which, I will say, came as a surprise to me, as I thought it would take place after results were in for the recent quarter – being acquired by Microsoft might now be a pretty good idea.”

Kevin Kelleher, GigaOm: “I think Yahoo investors would have slept a lot better tonight having read a single statement like this: ‘We thank Terry for his contributions as CEO, but investors with a larger stake in the company than he has have pushed him out. It may look like things are a mess right now - and they are - but we have a solid plan to right the company this year.’ Instead, we have corny PR.”

Pic on the right courtesy Thomas Hawk.

Alan Meckler: “Early on Yahoo brought in Tim Koogle to be CEO and then of course Terry Semel. I always wondered what Jerry saw in these people. I am sure they were fine business people but I always felt Jerry could have done better than any hired hand. Koogle made a bundle and Semel did even better. ... Now it is crunch time for Yahoo and the new captain is the founder of the company. Perhaps Jerry will be able to pull a ‘Steve Jobs a la Apple’—and bring back the glamor and originality that Yahoo had from 1994 until 2002 or so?”

Jason Calacanis: “What this move shows is that—like Facebook, Apple, and Google—the founders are often times the best folks to run the business. Wall Street and investors are too caught up in the ‘professional CEO’ who knows how to ‘talk to Wall Street’ and get deals done. The fact is our business is about one thing: product.”

Rob Hof, BW: “I sense that Yang has huge respect among the troops, and while he’s unproven as a manager of such a large company, Decker’s appointment as president signals that she will be picking up day-to-day executive duties.”