It's been mentioned a couple of times, but never been formally announced, so a lot of people may not know about it.
I know a lot of guys have issues registering for the Telkom/8ta Self Service. Earlier this year they introduced a new way of checking your balance: onnet.8ta.com.
It also allows you to get redeem airtime vouchers and buy data bundles.
What's important to note is that you need to be connected to the internet using the 8ta Sim whose balance you want to check. IE: If you want to check the usage of the sim in your ipad, make sure your wifi is turned off before you go to onnet.8ta.com.
It's a cool system, and removes (to a large extent at least) the need for remembering USSD commands and receiving SMSes. Also works a treat if your sim is stuck in a dongle or 3G router.