I've been on Hercules for about a month or two now, coming from rAthena. I haven't looked back since.
As a policy, they don't touch anything related to skills. At least, not yet. They're waiting on Malufett to finish up Renewal's attack formulas before going full blast on fixing skills. If a skill's broken on Hercules, chances are it'll stay that way until then. Still, the way they left skills right now's a lot more manageable than the hodgepodge job rAthena's done with theirs IMO.
There's also the odd bug here and there, (the more annoying one currently being item skills have requirements that shouldn't exist) but the development team sorts most of these problems out fairly quickly. Bugs are arguably fixed faster here than on rAthena, even. There was this huge bug with Homunculus S that I encountered and a fix was put in less than a day after I reported. When another bug came up, that too was resolved a little under a day after I reported.