I don't know if the two new females are better than Alisha, but they're pretty good. I'm not as big a fan of Finn or Alex, they just don't interest me that much. Rudy, though, just keeps getting better and better. The episode this season with the 3rd Rudy was fantastic.
I don't know if I like it as much as I did for the first two seasons, if only because there isn't anyone on the show that matches Nathan's electric presence. They've gotten way more ambitious with the format though. The Rudy ep was great, the zombie noir was crazy ambitious, and this last episode...seriously, only Misfits could do a story about a guy getting his junk stolen. I'm also really digging the new probation worker, he's delightfully wacko.