Yes, for the duration of the event. Once the event ends, you will no longer receive rewards, of course.
That depends on your level and relative power. So far, the events have benefited primarily lower-level players. Higher-level players tend to find more reliable success in PvP, and PvP rewards typically dwarf the bumps these events provide. Events have existed for Ultra-Rare event troops only, and (whether by luck or by design) the URs released for these events have not had much synergy with the existing troop list. (Runesmith, especially, is more or less worthless in a high-end deck.) However, they provide a change of pace, and many players appreciate an opportunity to flex their deck-building muscle when an event shows up.