Got my Engineer up to 20 and still having a blast. Good visual and sound feedback on abilities, great mix of abilities and lots of room for depth and customization. I really like the attribute implementation in this, theres enough room for customization without it being super punishing if you mess up. They got the right mix of everything. I see a lot of people saying the Berserker is one of the best melee class designs so I'm going to have to check that out. Mods will only make this better, I can't wait to see some new class designs from the community.
My group has room for a fifth if anyone wants in, hit me up on Steam.