One of my formulas has a "lowercase-L", which in the default font looks just like a "number one" and a "capital I".
Quick, what letters are these: l 1 I
This is pretty unclear lettering, in my opinion. Context is everything. To be distinguishable in a formula, the little "L" must have at least a hint of a curl at the bottom. I also don't want the upper-case letters to be excessively flowery. That just looks inappropriate in a serious work document, and some of them are hard to read.
I liked "Lucida Calligraphy" and "Lucida Handwriting" the most. Then I went Greek. Try putting in a nice Tau (τ) or Theta (Θ) here and there, and what you get is an empty box (□). Darn it. I'm not about to change fonts every time I need those. I seriously considered attempting to add "Lucida Sans Unicode" Greek characters to my "Lucida Calligraphy" font, but decided that was seriously going too far.
After hunting through the dozens of fonts, the only one that met my needs, although a tad on the flowery-side, is... (drum roll...):
|Here's an example using Monotype Corsiva for variables. They look more hand-written, which is also nice. In MathCad, to change the font for variables, select the characters of any variable and change the font; the whole sheet will update.|
Now, that was just more trouble than it should have been.
For normal text, I like "Calisto MT". It's a nice size, and has an "I" with crossed top and bottom.