I think Ulquiorra found Orihime fascinating ("What an interesting human/woman" -> "What a strong woman/that woman has a strong spirit.") Then, when IchiThing put the Cero through him and Orihime was crying for him to stop, Ulquiorra kind of...snapped? Not like "RAEEEAGGEEE" snapped, but something clicked in his head. Something so profound that he decided to get up and break IchiThing's mask even after saying he was beaten, and that his life no longer had meaning. I heard it best over on BA...when Orihime (again) rushed to Ichigo, Ulquiorra looked like a kicked puppy.
So, he turned his back to them all and contemplated his fate. When all was said and done, and he started turning to ash (and Ichigo refused to kill him so his death would hold some sort of value), he turned back to Orihime. He lifted his hand even after saying he didn't have the strength left to walk. He gave her one last chance to admit if she was scared of him or not, and seemed pretty pleased when she said she wasn't. Then, of course, her eyes start to tear up (fresh tears, mind you) and she reached back to him.
Kaien once told Rukia, "The Heart is born when you care for someone." I feel that this is what happened in this moment. The two of them had a deeper connection than either of them has had with anyone else they know, and it was suddenly being ripped away from them at the same time.
Do I think Ulquiorra loved Orihime? For the whole 15 seconds he had between "Are you afraid of me? Woman" and "I see, this thing in my hand is...the Heart" I feel that he very much did love her. She was the first soul he'd ever shared a bond with that didn't shun him right away, or use him, or threaten him. She was the sunrise that finally pierced his dark and sunless world. The speck of hope he never knew. She was The Heart to him. She was everything he ever wanted and never had.
Did Orihime love him back? I think yes. Not in the romantic sense, but the kind of love you share with someone you're good friends with. She did reach out to him once, before realizing he would turn to dust, knowing full well that if he hadn't, she would have been holding his hand (something she has never shared with anyone else
that was conscious and willing), and then reached a second time after he did start to fall apart, like she didn't want him to go. She cried for him. She mourned enough that even Ichigo noticed her feelings for once...and it was a powerful enough moment that Kubo thought it was important for Ichigo to reflect on some 20 chapters after the fact. However, in a sense, I think that Orihime has demonized the memory she had of Ulquiorra because her sudden feelings for him (however weak or strong) were enough to contradict her '5 lifetimes' statement from 24 hours earlier. Even if it hasn't been addressed in any fashion in canon yet, I think that her experience on the dome has somehow become the reason why she's overcompensating with her obsession over Ichigo in the current arc. I've seen many folks say they think she's hiding something...I think this is it. I think, if Ulquiorra had lived, Orihime would have fallen for him (especially since he realized what the Heart was,) and I firmly believe that it's possible she feels that this fact is/was a threat to her love of Ichigo, and now, she has to make up for it by being extra crazy.
I honest-to-God hope Ulquiorra returns to the story...if for no other reason but to help Orihime grow and be awesome again. If Kubo never has them get together...that's fine...I can still dream of their potential...but just physically having him there would do Orihime a world of good. He has a calming effect on her, much like how Rukia calms Ichigo.