We love homeschooling, but since you asked, here are some negatives:
no time to myself and it's a big ordeal to find childcare (no family here to help us). this is a big one for me right now - sometimes I'd like to take a nice long shower without having someone stick their lego creation in for me to look at.
sometimes the homeschooling community isn't very welcoming of a secular (and lesbian) family. We live in a very large city and I don't know of another gay/lesbian homeschooling family.
the time on the internet researching curriculums, styles, etc. can get a bit overwhelming.
for me, it takes a lot of time to plan and organize even though I would say we are very relaxed homeschoolers.
my house looks like an educational toy store - maps in our hallway, solar systems on my dining room table, etc.
loss of income, though I'm glad to not be working.
my son is gifted and I often worry if I am meeting his needs (even though that is one of the main reasons we decided to homeschool).
I'm homeschooling my 6 yo and I worry about what it will be like in 3 years when I am also homeschooling (officially, that is) his sister. Because of their age range and their differences in abilities, there isn't much they could do together.
that's all I can think of. my list of positives would be really, really long.