Curvature Combs and Tunni lines
Two ideas, both aimed at creating smoother curves:
an additional visual aid that could be enabled/disabled via hotkey or option on a panel that assists the artist/user in evaluating whether a curve is continuously smooth, or whether it needs adjustment. See this blog for a quick coded breakdown:
see this webpage for more traditional curvature combs with lines perpendicular to the curved path, in proportion to the path's curvature at that point:
an additional assist/handle for helping a user more precisely adjust a curve (or multiple curves), both symmetrically and asymmetrically.
See this example as implemented in FontLab:
See this webpage for another examples, of each of these ideas:
Note that I'm not suggesting that the illustrator team rip-off anybody else's software, but I think these sorts of tools/assists would be handy for quite a few users who require more than the typical "eyeball-it" precision illustrator offers currently.
Konstantin Malaev commented
Please! Please! Please! I'm begging you! IS there a plugin for this???
Very much yes.
There is a chance there might be a external plugin for that, but so far FontLab stays unchallenged here.
I wish for more demand in this field.