I'm going to take a guess here and say that while it does reflect some psychological issue of Ichigo's, probably some combination of suddenly having a Hollow hole and his single-minded desire to protect, it DOES NOT reflect a sudden increase in power on Ichigo's behalf. Rather what we are seeing is how powerful Ichigo truly is and has been all along.
Basically the reason I'm saying this is that Ichigo has consistently shown sudden and truly massive spikes in power followed by what can be later considered truly underwhelming performance when all the facts are assembled. First we have his regaining his Shinigami powers after his first encounter with Byakuya. Specifically he burst out of a Level 99 Binding Spell cast by someone who we would later learn to be the former Captain of the Kido Corps. Then when he first learned Zangetsu's name he unleashed a Getsuga Tensho that cut through a protective barrier cast by a former Captain and gouged what can only be called a small canyon into the ground. This represents a display of power orders of magnitude greater than anything he displays until achieving bankai which brings me to my next point.
After achieving bankai and when he fights Byakuya it is noted that Tensa Zangetsu grants him super-speed that surpasses shunpo. And since we later learn that Byakuya learned his shunpo from Flash Goddess Shihouin Yoruichi that says a lot indeed. Even ignoring his initial fights with Grimmjow and Ulquiorra since he was concentrating on controlling Shirosaki, his fight with Dondorii and his final fight with Grimmjow he displays none of that super-speed while using bankai. Even with his mask out while fighting Grimmjow they're a close match in speed while Byakuya, who first noted the super-speed aspect of Ichigo's bankai, is able to out manoeuvrer Zammori, the fastest of the Espada.
To summarise, Ichigo has displayed tremendous power at various points in the manga up to this point, but his failure to do so consistently leads me to surmise that on some level he's been suppressing this power for whatever reason. However the single-minded nature of Beast-Ichigo has removed these psychological blocks and given Ulquiorra and us a taste of just what Ichigo will be capable of when he fully masters his power.