Each time the smarts is restarted, the default setting is active again. So it is, as if you had no regen paddles. If you pull on the pedals, the recuperation becomes stronger or weaker. If you do not want to use your foot to dose directly to the gas pedal, you can do so with the regen paddles.
Basically it's a 50/50 thing whether you like it or not. Personally, I'm not a big fan of it, but there are certainly people who like to play with it. Just try it yourself.
If you've got the smart ED3 Brabus, you've also got the "sport"-mode. With this mode activated you'll get the full regen just by lifting the food off the pedal. They also shortend the pedal travel, in the "sport"-mode you'll already reach foll power bevore hitting the kick down point.