You are not the only one. I've used proportional fonts exclusively for 10-15 years and will never go back to monospaced.
In the past I used Verdana, Georgia, and Trebuchet MS. That last one may seem like an odd choice, but I really like the way it renders on a high-DPI display, with thick readable strokes and easily distinguished "confusable" characters.
Trebuchet MS does have some flaws, so I started customizing it into what I call Trebuchet++. What got me started on this was the poor tilde in TMS. I swapped in a better one with FontForge, and then started experimenting with a few other things.
One thing that bothered me in particular about proportional fonts is that the underscore character is so much wider than a period. This creates the wrong visual grouping in something like this:
name_with_underscores.method_with_underscores()
The default spacing causes "underscores.method" to be bound tighter visually than the individual names on each side.
So I edited the underscore to add negative spacing while keeping the underscore itself fairly wide. And I added positive spacing around the period. This makes it more clear visually that "name_with_underscores" and "method_with_underscores" are individual names separated by the dot.
The next tweak I plan on is adding some positive spacing after a "(" and before a ")" and similarly with [] and {}. It makes me sad that modern coding standards prohibit spaces inside (), [], and {}, even though it makes so much sense logically to have spaces inside them.
If I can't fix my company's mandatory code formatter, at least with a proportional font I can adjust it to put just a bit of whitespace there.