turns out, my frustration for the past several months with this mouse was due to a bit of fuzz stuck quite firmly in the optical sensor. Blowing wouldn't remove it; we had to use a canned-air duster. And now it's so smooth and unjumpy!
@Efi Our mouse isn't easily disassembled, unfortunately :< The wheel is particularly bad (it's kind of corroded) and we'd like to replace it, but it's not easy to find a replacement part.
@Efi We use this for CAD work, so we need more than the usual number of buttons. Also this wheel lock feature that the logitech G700s has is too good to give up ;.;