*Angela*, you like Jiro less and less as you get to know him? O.o; And yesh! You're right, I'm gonna rebut. ^.^
1. He's not happy in Fahrenheit? lol, Silly, Angela. Jiro is so so dead tired lately, he's getting like 2-3 hours a sleep a day only, he care barely stay awake, that's why.

In fact, normal beings would be grouchy and annoyed even when they have THIS little sleep, and you have big bright lights on you, people taking pics, interviewing questions, always think you're bitter with your friends in Fahrenheit, etc---this all boils down to a very stressful and very tiring for Jiro. Calvin is still smiley and okie most of the time because he's the only member of Fahrenheit that gets more breaks than the rest. Aaron is busy lately too, but he's usually quiet so the change is not as noticable. Wu Zun is busy too, but he's known as the "strict" daddy in Fahrenheit, so he's usually not all crazy energetic like Jiro, so the contrast isn't big either. But for Jiro, it just looks like a big difference.
Also, I think Jiro's really friendly with everyone in Fahrenheit!

In fact, he's like the one who connected everyone together when they first formed. Meanwhile, it's actually Aaron that's less close to everyone else, not Jiro. Aaron is kind of quiet and keeps thing to himself, and doesn't related to the others much, but it is Jiro who reaches out and cares for Aaron, so that's why Jiro appear especially closer to Aaron than the rest. Also, since Calvin and Wu Zun easily became good friends already, so to our eyes, Jiro doesn't seem as close to the other two, but he's actually really friendly with everyone.

2. His singing got worse? Which song(s) are you referring to? I thought he sounds terrific in their second album!

it's so soothing and more angelic than ever to me!, lol so I'm not too sure what you mean ^^;; Maybe you could tell me?
3. As for the attention speaking part... This is strange. When he's happy and go lucky, people think he's attention grabbing, but when he's silent, you think he's not satisfied with Fahrenheit? Sometimes nothing satisfies people, huh? O.o On Jiro's blog, he says one of his hobbies is to serve people, as in to entertain people and make them happy. I don't think he's attention seeking because he's simply doing his job and having fun
entertaining people. It's like accusing Calvin is attention seeking when he talks a lot ---- and Calvin does talks the most because Fahrenheit finds Calvin as the most diplomatic one and have him speaks the most to explain things or tell stories, but it's not true, right?

They're all being themselves, and doing their best as entertainers. Also, Jiro is usually like a big little kid with so so so much imagination in his head, so he acts like a kiddy sometimes when he speaks his mind which makes people think he's attention seeking.
Honestly, I think Fahrenheit would be just another typical Taiwanese group without Jiro. Without Jiro, it'll be another mature-ish type group like 5566, 183 Club, etc. Like, their first main song, "I Have My Youth" I think Jiro is the leading spirit of it. I mean, you gotta agree that Calvin and Wu Zun are both very mature people (both in age, and mind). Aaron is young, but he acts really mature for his age, like he ruminates on life, and etc. But it is Jiro that carries the most youthful spirit, acting like a kid, but yet like the idea of growing to be a man, making it a versatile group about both maturity and youth.
Also, for some of the critics, it's also really really not fair to pick out the OLDer variety shows and say Jiro is attention seeking there. When Fahrenheit is new, everyone except Jiro is new!

They're all shy, and not sure if they're saying the wrong things, so they rely on Jiro to lead them through the show, and he tries to make it light hearted to get his fellow members more comfortable and have fun. It's a little sad that Jiro is being blamed for attention seeking when he's just trying to be lively and active to invoke the other members to get going. ~_~ From what I see, now that everyone in Fahrenheit is more used to being idols, Jiro is no longer as lively like that anymore; not that bridge connecting them to the entertainment world anymore. In fact, I kinda miss seeing him active and yappy on those variety clips and shows now, he's a lot more quiet in comparison now ~_~
Eek-ness, sorry for writing so much. I wonder how many people just skipped right over my post because of this?

;;; lol! I hope not, I took a long time to write. haha ^^;;;