As an initial matter, I think that the hope of working in biglaw/getting the big salary is not a particularly good reason to go to law school, especially from a lower ranked school where it can be true crapshoot to even get the job. On the other hand, if you are at a T14 (or really T10) law school, you can generally get a biglaw job pretty easily if you are not a total idiot and/or extremely socially awkward. This was mostly true even during the heart of the recession. So, assuming you can get the job, is it worth it?
Totally depends. I worked in biglaw for two years before switching to the government. I actually never really wanted to work in biglaw, but it basically turned out to be easier to get a job in biglaw from my T10 law school during the recession than it was to get a government job, probably due to all the state and local budget cuts. So biglaw is where I ended up. It was fine, but perhaps only because I basically had one foot out the door right when I arrived. I said no to stuff, didn't work on weekends unless someone directly asked me to, didn't bill a ton of hours (probably averaged about 1750 hrs/yr) -- probably not things one would want to do if they were trying to make partner. That said, I got great reviews (pro tip: reviewers can generally only really judge you on the work that you do, not on the work that you don't do) and the partners I worked for have been excellent references now that I've moved on. Also, the resources and training were really very good, and I was able to pay off all my student loans, put a down payment on a house, and save a decent amount of $$ over the two years I was there (of course, I have a wife who also used to work in biglaw, so results may not be typical). At the end of the day though, I really did not like the work at all -- mostly very tedious (as a lot of legal work is) and very unsympathetic clients (mostly big banks and other financial institutions in my case). On the other hand, I love government work, even though a lot of my work is still tedious and I get paid less than half as much as I used to. The primary differences for me are that I generally really believe in my clients and their mission now, plus I have the luxury of a real 9-5 job, which gives me some actual time to spend with my wife and young kids, do some structured training, etc. I don't regret my time in biglaw, but like I said, I knew I was getting out.
As I mentioned, my wife also worked in biglaw (for almost 5 yrs), though unlike me she signed up at least open to the idea that she would make a career of it. She did really well too, and was identified as a "rising star" and put on high profile cases with high profile mentors (who, to their credit, really did mentor her), and...she hated it. I am pretty confident she would have made partner if she stuck it out (she was already responsible for some big clients at the request of those clients, etc.), but it just was not worth it (mind you, she averaged about 2500 hrs/yr, and probably peaked at close to 3000 -- that will crush all but a hearty few). It was so bad, she almost left the law altogether, which would have been a shame because she is such a great lawyer. Thankfully she found a good gig in-house, and is now pretty happy.
So, I think biglaw as a career can be worth it if you really love the work (and some people do!). But, if you're doing it just for the money, or because you have this vague idea that it will be "interesting" and "prestigious", I think you're more than likely to burn out. In my experience, the partners that were truly successful basically lived and breathed their practices -- everything else, including family, was secondary (if it even rated at all). If that is not you, I think biglaw is a bad bet for the long haul.
I also think biglaw can be a great stepping stone to more satisfying and humane work with the government or in-house, particularly if you don't have a family, but beware of the power of inertia. Plenty of my classmates (and even some of my wife's, who have been practicing for several years longer than me) are still in biglaw even though they really hate it and want to leave, simply because they can't get it together to even look for other jobs. Also beware of the "golden handcuffs" -- another friend desperately wants to leave biglaw for government, but is basically trapped paying for a nice Manhattan apartment, huge student loans, two kids, and a stay-at-home spouse. He's in it for the long haul, but not really by choice.
Good luck!