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two weeks ago I applied to a biglaw firm in a secondary market.
By way of description, the city is among the 10-20 largest in the country, and there are approximately 10 firms with over 100 attorneys in town.

I do not work for a firm of any particular note, but my specialty is in high demand, and roughly half of those firms are looking for someone with my experience. I've been overlooked by a few of those firms, as I do not have the right kind of resume to get past the gatekeepers.

One of those firms (rank 60-80 in the country by headcount) gave me an interview last week, with the co-chair of my department, who reiterated that my specialty was in high demand and explained exactly how I could fit in the firm and help them. She did tell me that they only just started looking, and that a firm that size moves slowly, so it'll take a while.
Earlier this week I received a good offer at a respectable boutique, which I am happy to receive. I contacted HR at the big firm, and before I even said why I was contacting them, HR told me that the co-chair liked me a lot and gave me more positive feedback. I explained that I got an offer, and was told by said HR that she'll be in touch with me ASAP.

Can anyone provide any advice, comments, suggestions, anecdotes, stories, anything that would make me a little less nervous about this?

[+] Spoiler

I still don't know if I'll be able to get the job - my resume and experience is not the traditional path for biglaw, which is why some of the other firms never even gave me an interview. That being said, at least two of the firms that passed on me have been looking for over 6 months, and I know for a fact that for my specialty, attorneys everywhere are swamped and that a lot of firms have been turning away business because they don't have the capacity or the expertise.