It's not like Aizen disappears. He just is somewhere else. Of course he'd be visible for Komamura. Was it the real Aizen, though? Yamamoto could tell it's Aizen only because Aizen stabbed him. I don't think it's any feat to grab a guy who's stabbing you. Zaraki could dodge attacks because he felt them touch his skin and avoided fatal wounds. Yamamoto was stabbed, and then he grabbed it.
Fooling whole SS (Unohana excluded) about him getting killed, made G13 believe some guy was him during TBTP, in FKKT fought whole G13 and survived because he used KS. He didn't escape with his power. His KS IS overkill and hax, but it's not made for simple 1v1 battle. It's made to fool lots of people at once. Hell, he could create his image and make Ichigo fight illusion, then stab him like he did Hallibel. Then he just needs to run away from his range and use his ability again. Nothing easier. Remember what he did to Barragan? He made it look like Gin and Tousen are just standing there, while they exterminated his army. Which doesn't mean it sux in 1v1. It's not giving him any direct advantage. But if he makes someone fight an ilusion... Or make his Kyoka Suigetsu a fake Aizen (as he did when he met Unohana), he can make anything, against anyone. He could even fool Juha.
We don't know if he presented his Shikai. He presented KS, and if it's Bankai, he presented his Bankai, but made it look like it was flowing water-type. I don't believe myself that Aizen showed everything, it'd be too lame. He'll be the final villain after all, he needs to mindfuck a little. Yeah, I think Juha won't be the final boss.