Make sure you start to read up on all things gifted including the possibility of "overexcitability". Since learning about that I can be so much more supportive of my DS4's sensitivity to noise etc.
When DD was 3, we took her to a Doodlebops concert, and we were there for maybe three songs before she asked if we could leave, because her ears were hurting. DW was furious, because we'd spent all that money on tickets, plus drove an hour. I just hugged DD and told her it was okay, because my ears were hurting, too.
DW does not share our sensitivity to sound, but foul smells make her physically sick. I could never understand why she'd run the bathroom fan 24/7 if I let her. Now, we all understand each other.
And about the talking, DS4 was not an early talker. At age 2 he would say 6 word sentences but he didn't really start to talk until about 18 months. Being bilingual MAY have had something to do with that though.
Definitely. There is tons of research that supports the idea, because bilingual kids are simultaneously absorbing two different linguistic sets, with all the sounds and grammatical rules those entail. They typically speak later, and then they take off like rockets in both languages. This is true of normal children as well as gifted children. My wife's brother has a whole brood of bilingual gifted boys, and we've seen it in all of them.
In fact, I'd attribute Cheri's observation of apparent non-giftedness in speech to bilingualism, because if Rory can make herself understood in sign language, that means there's less urgency to work on spoken language. Rory is absorbing the concepts of both, and will likely take off in spoken language very soon.
My DD went the other way... we originally planned to start teaching her baby signs at 6 months, but by the time we got there, she already had spoken words for everything she needed, so we threw away that plan.