I just upgraded to Ubuntu 15.10 (wily).
I notice that htop no longer shows the percentage numbers for CPU, memory and swap.
Is this a bug or "the new" way?
htop author here. This is most likely a problem in the way your terminal handles gray text. In terminal ANSI colors (man console_codes) gray text is made by combining black foreground and bold, and this is what htop uses. However, some terminals display this combination as "bold black", rendering the text invisible when written over a black background.
In the version of htop currently in git, there is a "Broken Gray" color scheme, that is identical to the default, but does not use gray at all. You may want to use that, or try to configure your terminal colors so that it properly displays gray.