Once again, it's important to distinguish between biglaw prospects and prospects in general. Sub-3.0 is going to make biglaw pretty difficult (but probably not outright impossible) from a lower T10. Your chances really do improve dramatically, though, if you're willing to consider quasi-legal jobs, jobs paying between $50,000-100,000, and jobs in a diverse geographic range of markets (especially if you have a connection to one of them). Your chances of getting a legal or a quasi-legal job paying $60,000 in Detroit if you went to Michigan and are from Detroit (or a nearby suburb) are very strong, for example--and will be pretty much no matter where you finish in the class at Michigan. I think dropping out would be foolish if you (a) like it enough, and (b) are considering accounting as an alternative: I think your chances of getting some semi-interesting $50-100k job will be much higher as a bottom quarter T10-er than as a median accounting graduate from a comparable school (and let's be honest with ourselves -- the skills necessary to do well in accounting school aren't all that different than those necessary to do well in law school, so chances are you're not going to be bottom quarter at Michigan Law and top quarter of a comparable accounting school).
I also want to add my voice to the voice of others in saying that your chances of anything (biglaw or just some other adequate employment) are going to be pretty substantially influenced by your charisma and somewhat influenced by your race. If you're a charismatic URM, my guess is that biglaw is a real option even with a sub-3.0 first-year GPA (even more so if you have impressive pre-law credentials -- a 3.9 from Princeton, for example). How you interview, and the rest of your resume, really is going to factor into your chances in a situation in which your grades aren't up to snuff. Biglaw hiring is mostly grade- and school- based (and for some firms, that's all they are), but most firms will make exceptions to their informal grade cutoffs every year for the right candidates. (And I don't mean to discourage you if you're a pretty average white dude: I still think your chances of *some* quasi-legal $50k-100k job *somewhere* in the country are really pretty good.)
Finally, and I think this was to a poster other than the OP, if you scored in the 99th percentile on the LSAT and had a 4.0 GPA, you probably do have most of the skills necessary to do well in law school. Assuming your undergrad was legit and you have some aptitude for the law (you probably have some idea of whether you're just really not getting things, or if you're underperforming your true ability on the tests), then I'm betting your grades will go up as you continue in law school. 1L core classes are a somewhat unique beast, and as you are able to branch out and take a greater diversity of other classes -- trial ad, paper classes, clinic, etc -- I think you'll see whatever it is about 1L classes that is throwing you for a loop become much less of a factor in your grades.