I avoided this thread because my opinion is that anyone who needs to ask this question probably shouldn't buy a birkin. However, it seems to crop up all the time and finally I clicked on it. Plus, it has been quite a lovely day and I've thoroughly enjoyed the weather with a lovely meal with friends and a few too many glasses of well chilled white, so here goes...
Is it obtainable - of course! There is no secret handshake which one needs to learn in order to obtain a birkin. Enter shop frequently, ask politely, and chances are that you will happen to chance upon a birkin. If not, there are reputable resellers which have a varied and plentiful stock of birkins.
Is it worth it, really a difficult question to answer. Worth is something which is extremely subjective. My DH collects photography and spend many multiples of one birkin price on one photo. Is it "worth it"? To him, yes. To me, not always. I mean, at least a birkin is useful and practical - a photo just sits on a wall (or, in his case, more likely in a portfolio). However, the pleasure he has is in hunting down, acquiring, and looking at said photo is priceless.
Different people have different reasons for wanting a birkin - all legit. Doesn't matter if some want it for the prestige and others want it purely for aesthetics and for the sheer craftsmanship. Usually it is not just one factor which make an item "worth it", but a combination.
Most people bristle as this question because it implies that their reason for buying a birkin as opposed to an almost similarly crafted, but not as expensive or difficult to obtain bag (not in the league of TJ Maxx, but more like Celine and such) is simply because the purchaser is shallow and has more money than sense. I don't blame them.
Final answer, is it worth it - to me, yes.*
*Yes, I am well aware that the mark up on the bag is astronomical and that H is brilliant at marketing and that not all is exactly according to the mythical story of the making of the birkin...and so?