Easy change to improve the programming interface: use a font where all of the characters are unique. In the font that's used now, the l and 1 look the same. There really is no reason to use a defective font.
The font can be changed by editing the preferences.txt file. I changed to Consolas and I can distinguish lower-case L from one.
But, regardless of the font, visually it's choppy, not very smooth. Am I the only one that has that problem (on Windoze)?
Thanks, Jack. I can use that.
Still, I think it would be worthwhile to change the standard font to one where no characters are identical. I mean, changing my prefs won't change how other peoples' code looks online. 
Yes, please change default font or size.
I've started use the arduino platform today.
After installation the default font size is 12
The problem with this size is:
Number "1" looks like lowercase "L"
This take me a 2 hours to figure out what I'm doing wrong in sketch.
Change it to 13 or 14, the 1 will look different at a slightly larger size.