I'd like to know if it's possible and if it is, how complicated/hassle free is it compared to doing PhD on F-1?
Thanks.

Its not complicated at all....in my case after doing some communication with International Student Affairs, Office of graduate Studies, and the department i got enrolled in; it turned out that my official legal status will still be H1B and International Student Affairs do not have to issue I-20 and F1 status since it will automatically discontinue the H1B if applied. So the office of graduate studies enrolled me as a grad student i.e. gave me an official admission and i went from there. Rest is same as a typical international student which involves non-resident tuition. for info. regarding how to manage tuition fund and research hours funds, you can ask me later when time comes.

Good Luck, u gonna be pretty busy. having GF in long distance will make it worse.

I thought the subject of PHD was H1B

 thanks for the quick response and the info, poon_hill. i have a follow-up question - do you know anything about extension (H1B) beyond 6 years? I'm sure extension after hitting the 3 yrs mark isn't a problem. But what if, for some reason, someone fails to complete their PhD within 6 years? Is it possible to extend further, or can one apply for a F-1?

kiddo, i don't think they teach H1B to PhD students 
elaborate? i'm having hard time understanding what you're trying to say, bro.

I think you can change your status to F1 easily and continue studies after hitting 6 yrs H1B thing.

 Thanks again for the info. I'll now go ahead and confirm with an immi. lawyer before I make up  my mind to atart H1B petition. I wouldn't mind staying on F-1, but I hear that it's much easier/simpler/likely to get a dependent visa for spouse with H1B.