It really depends on who you ask. I have almost always glued together my models before painting. I do not have a problem with that. I do know some guys who prime and paint their models on the sprue, then put them together. I prefer to glue mine up front.
Some areas are easier to get to when the models are not put together. Beyond that, you should have no problems.
As long as you do alright handling the minis when painting you'll be fine! Like Arli said, some hard-to-reach areas may be kinda tough, but don't worry to much about it.
Anyway most of the hard bits to get too are not going too be seen so it makes no difference unless you paint for a competition, and me i have always glued then painted.
The only parts I don't attach before painting are shields, because it is quite hard to get underneath them. Other than that most areas are pretty easy to access.
Same here, although the same goes if there's any other parts that may create a risk of spill, like those wretched Halberds Temple Guard use. Cheers!