Screwed by the Network: the show was put on Saturday nights, then bounced around ABC's schedule until it was just cancelled.
Word of God: In an interview Thomas said that the series would have ended with Cupid's nature left ambiguous; he'd have "given up" his divine nature to stay with Claire, but we'd never know for sure. See Maybe Magic, Maybe Mundane.
Actor Allusion: A really unusual one: actress Anna Chlumsky had a bit role in the first series, and has a recurring one in the second series.
The Other Darrin. Out of necessity. The original cast from the 1998 version of the show are already involved in other projects (plus they're all ten years older).
Screwed by the Network: Debatable; it was put on after Dancing with the Stars which is arguably a decent lead-in, but 10 pm is never a good timeframe for a brand new show, and they pre-empted it with The Unusuals at least once during its first run.