I can't say it was as user friendly as previous versions
You can't say being unable to change anything but background colors and some fonts is user-friendly either. I agree editing XML is not much fun, but now we have complete control over the appearance of the panel. (It helps to use something like
XML Notepad for editing XML.) For example, global fonts and font attributes are set in the <labelfont> and <fieldfont> sections. They can also be set on individual items...
<fieldname>
<font>
<name>Calibri</name>
<size>16</size>
<color>$FF0000</color>
<bold/>
<italic/>
</font>
</fieldname>
I tried to change the customsection color and that didn't change in the database.
As a "catch-all" for custom fields which haven't been explicitly placed elsewhere in the skin,
customsection is likely to behave differently. Even if you want all your custom fields shown together, I recommend defining them explicitly in a regular section—so you can have control over their appearance and placement.