Well there are a few oddities that may be brought up like why Sakura's new abilities were not utilized against Sasori as that battle was fairly intense and she was on the verge of dying quite a few times there. However, what others fail to take into consideration is that Sakura has been having to accumulate chakra into her forehead for three consecutive years before she could finally materialize the seal. It would have been impossible for her to use a rudimentary version of it as the seal must fully accumulate chakra before it can be used.
I agree that there could have been some foreshadowing throughout the manga to establish that Sakura was gathering strength for an unforeseen new technique; a "that jutsu" for herself,if you will. But Kishi chose to finally reveal it in the manner that he did and I wouldn't necessarily refer to it as being contrived. Sakura's proficient chakra control abilities have been complimented several times in both P1 and P2. Furthermore, it has been suggested on a few different occasions that Sakura had the potentiality to surpass Tsunade. How would she do this, you say? By inheriting her teacher's abilities and honing them with her own personal strengths.
Really, how does this appear any more complicated or forced than Sasuke miraculously summoning a hawk during his battle against Danzo or the rookies illogically acquiring the ability to use nature transformation for Doton ninjutsu, an advanced method of chakra control, without any prior instruction given to them being suggested? Do they berate the characters involved with these "asspulls"? Well I have seen them do so, yes, but not to the degree which they denigrate Sakura but that's to be expected as they simply do not like her character no matter what she does or how much character development she receives. Several of these people have openly admitted to this on other forums.
I say let them revel in their own world of false impressions and embitterment as they obviously don't appear to be concerned with what other people say or even with what is being depicted by the author.
Edited by Atheck, 01 June 2013 - 08:06 AM.