I voted not exactly because it's not turned out as it had been proposed. It's not a place for non-/qa/ things, I really don't see that, and it hasn't drawn serious discussion. I'm not even sure it's made /qa/ slower, but I don't have any prior data to compare with.
I got some metrics out of the boards:
average of 12.75 posts per thread
threads below that: 98
threads above that: 48
so about two thirds are below the average of replies and one third is above it
threads above 50 replies: 13
total replies of those bigger threads: 1248
which is about half /qa/'s current posts
I put 50 as a threshold because there's a jump there where threads become much bigger, although it's rather arbitrary
oldest thread: made 3 months ago (putting the happenings general aside)
currently closest to death: made 19 days ago
average of 3.78 replies per thread
threads below that: 80
threads above that: 54
this one's about 3/5ths and 2/5ths
threads with 10 or more replies: 12
total replies of those bigger threads: 173
which is about a third of /jp/'s posts
same thing as the previous threshold, kinda arbitrary
oldest thread: made 16 days ago, first thread made
currently closest to death: the same one
no threads have died on /jp/
Not sure whether that has any meaning, it's just stuff I wanted to check. It does make clear /qa/ has more centralized posts, although in this brute manner I include the couple of imagedumps that have done in /qa/, which are about a hundred posts of exception.
Anyways, what I'm not sure of is whether those five hundred posts made in /jp/ couldn't have circulated through /qa/ as small threads. But I don't think there's a way to know for sure. /jp/ did enable emoticons and text art to become more popular, and that's nice.
manual count shows that it's reduced speed a bit. /qa/ threads are more focused in my opinion and people who want to post simple one day threads have a place to do it without slower ideas having to compete.
I don't think that /qa/ has really reduced speed as a result of /jp/ but instead has just slowed as it's a slow period. Comparing /qa/ alone to ota shows that the two are relatively close in activity and ota has slowed down quite a bit as well too. So this would normally be a period in which kissu would be getting around 100 posts a day, but with the use of other boards it's regularly still hitting 200+
This is the problem of counting activity by post numbers. They don't really mean anything and are subject to season and time more than anything that site owners have control over.
Even if /qa/ were slower, this is what some people have been asking for, and from what I counted the overall board speed is still expected and acceptable.
Improvements to /all/ were requested by two people and done quickly so I don't think it had any impact in the end of the day.