Roboto is reasonably boring but the real issue is, on most Android phones it’s the only decent font, so it’s a bit monotonous, but as a font Roboto’s fine.

However the Droid Serif font that ships with Android isn’t boring — it’s just awkward. Blockier than Times New Roman, with serifs that jut out. Reading a page of text in it does make me notice the font — and not in a good way.