ok, one reason why it is hard is because you have to find time to do it in between your other assessments. unless you're EXTREMELY disciplined, you're going to end up not looking at, let alone working on, your major for weeks on end during half yearlies, trials, and other heavy times. since it generally the last thing you have due, it often ends up as a low priority when you have craploads of other stuff to do.
also, just because you thik you know what you're doing now, doesn't mean it'll stay that way. theres a high likelihood that your idea will evolve or change completely between now and the due date, often meaning that at least half the research/work you've done will become completely useless to you.
another thing is that you have nearly a year to do this, so it's gotta be done well. it's one thing to bodge through an assignment you've had for two weeks, but your major is a big thing, and there's really not an excuse for it not to be great. and once you become attached to your work, editing can become really hard. even harder is when you just can't get into 'the zone' for writing - i know i found that for a while i could only work on my major after 11pm, it was the only time it would "write itself" if you get my drift (and i did a critical response, i imagine those doing poetry etc may have had it worse).
and no matter how well prepared you are, the final few days, especially the weekend before the due date, are going to be stressful. there will be panic attacks, just check the posts around here from that weekend (sparkly wig anyone?). and then you live in fear of finding a typo i your beautifully bound work - i still haven't read mine for fear of just that, especially since i've been told there's 2 little mistakes in it.
so overall, ext 2 isn't as easy as you might think, but that doesn't make it not worthwhile...i guess you get out what you put in, or another cliche to that effect