The thrice-monthly format wasn't the safest choice available for Marvel. Fans used to the monthly schedule were more likely to drop Amazing Spider Man if they were unhappy with events in "One More Day" given the significant drain on their bank accounts. Encouraging readers to buy so many Spider Man books every month was hell on the wallet. It also discouraged readers from picking up arcs by creators they would ordinarily follow if they had no interest in the work of the other creators. At the same time, readers who disliked one creative team were likely find themselves compelled to buy every issue by the team because of the way those issues would impact the work by the three writers they liked. This sucked for the reader, but didn't represent a problem for Marvel. Unless it made the reader's decision to drop the book easier.
Given how risky the venture was, the potential that readers would already be put off by the developments of “One More Day” and the much higher monthly cost of the series (as sales figures indicated that not everyone who buys Amazing Spider Man bought the side titles) Marvel could have chosen more commercial writers and initial storylines. No one would argue against artists like Steve McNiven and John Romita Jr. being qualified, but if your top “name” writer was Dan Slott, you were not playing it safe. Bob Gale’s comics credits were minimal and fairly unexceptional. Marc Guggenheim had a critically acclaimed flop with Blade. Zeb Wells had written plenty of solid Spider Man stories, but it was entirely fill-in work or tertiary projects (mini series, Marvel Adventures, etc).
The storytelling approach of introducing new villains for the next six months wasn’t as safe as pitting Spider Man against his best known enemies. Steve McNiven drawing Spider Man VS Venom is an easier sell than Steve McNiven draws Spider Man VS some guy you’ve never seen before. I understand why they did it. It was part of the process of slowly rebuilding the rogues gallery, who had lost their grandeur when a battle with Doctor Octopus became a visual shorthand for Spider-Man having a completely ordinary day. But it was not a safe approach at such a precarious time.
However, it worked. As I described in the months after One More Day...
At the moment, I am optimistic about the success of the experiment. Many of the problems I cited would still exist with the traditional format, especially given how interconnected the Marvel universe has become. Artistic consistency is more of an illusion, and now you’ll usually have one creative team on every Spider Man issue for a month, so the readers who picked up every Spider Man issue on the stands would have a better time and there wouldn’t be the confusion you get trying to follow the same character in three different monthlies with their own situations and longer storylines. Delays and clashes between creators are always possible, as long as more than one guy’s working on the Spider Man books.
Given all the disadvantages, if this project is a success, I would argue that it is an entirely unambiguous one and proof that the customers are happy with the new developments. It would be good in the long term, produce new villains to trouble Spider Man and other Marvel heroes for years to come and cement at least a few of the writers (if not all of them) as A listers, which will help their next projects. On the other hand, opponents of a newly single Spider Man (or whatever status quo occurs in "Brand New Day”) would attribute the success to the outstanding artists and Marvel’s cruel decision to “force” readers to buy three books a month, so the truth wouldn’t be universally acknowledged.