Vodafone and 3 merged last year, but it has taken a while for that to be evident to most customers, in part because of a commitment to maintain existing plans for both customers. A rejig of postpaid plans today sees common terms and conditions for Vodafone and 3 customers, but we still haven't reached the point where customers can call each other for free across the networks.
Nick over at Gizmodo attended Vodafone's launch earlier this week and has a pretty comprehensive analysis of the changes. The per-minute calling rate for the new plans (90 cents a minute with a 35 cent flagfall) is pretty high, but some of the other changes, such as allowing international calls within the cap total, could potentially be useful. Less impressive is the 50MB of data bundled with the plans, which is fairly low considering what Vodafone offers on its dedicated 3G broadband devices.