Glad to hear that Hutchison Group will operate their mobile network in Jakarta soon. Branding with name "3" - Three (applies to other countries too: UK, Australia), I believe it will bring a new competition to existing 'local' GSM operator (XL, Indosat, Telkomsel). With international expertise and competitive pricing, it will grab a lot of subscribers.
In the news that I read, call among 3 - Three - users is Rp 150 (local and long-distance) . Cross-operator call is Rp 1000 (USD 0.11) for local and Rp 2000 for long-distance call. No pricing for 3G Data communication yet, but it must be very cheap to attract 'internet-hunger' customer like me.
Another incentive should be phone-bundling, which is a common practice for Hutchison in US and Europe. This means you can get a new phone for free for let's say 1 or 2 year-contract.
One point is the service will be available only in Jakarta. For those of you outside the capital, be patient please :)
(update April 2) I've purchased a new 3 SIM card, its number prefix +62 899 XXXX, and the signal quality is very good in Lippo Karawaci and Kebon Jeruk, a good start for a new operator. But when I tried to open the website, it seems that it has not ready yet.