I've used twitter feed for years now, posting to my forums twitter and FB pages automatically.
I personally think its one of the best options for automatic posting, as it uses your RSS feed for only the forums you choose, posting at the interval you define. I've used nearly all presented here as add ons over the years, and none have lasted the duration. Twitter and FB have changed their protocols lots over the past years, and that has really made it hard for developers to give an effective solution to date. Twitterfeed negates all these issues... set and forget, never worrying whether twitter or Facebook change a protocol... because TW uses your RSS and they worry about the protocol integration with social networks.