I am not in the category you were soliciting responses from, but I have several friends that are mid 30's-40's and none of them had any problems getting interviews or jobs (when compared with younger students). Not only do they have impressive resumes full of work experience, but they are a lot more mature then the typical 2L. It seems like non-traditional students are ideal for law firms as most of them have the resumes together and are less likely to just be doing the big law job, in specific, temporarily.
I'll be 30 when I start work--6 years of experience with a consulting firm really helped me, everyone with whom I interviewed commented positively about it. But there's a certain age where the biglaw sweatshops may start to question your willingness to put up with the long hours and BS of being a junior associate. What age that is, I'm not sure. It's probably more like 45 than 35. And if your prior work experience is at all comparable to work you'd be doing with the firm, I don't think it will be an issue at all.