IS runs their service (especially the Business ADSL) through their satelite network and does not shape like SAIX. You will get some latency because of this.
Haven't used Skype yet over ADSL, but I don't think it's shaped THAT bad is it?
AFAIK IS is not shaped. Their is latency though, due to the satellites.
What this means is that you will get lag on international gaming, but p2p is better (once the connection is set up and pumping, it keeps a-going)
I have not tried VOIP internationally, but would expect a bit of lag (like on shaped SAIX), but better overall quality (once a stream arrives, it does not get flugged by SAIX).
we use both Skype and SIP call to landline/cellphone on IS ADSL, qualities are definitely much better than Telkom's ADSL, on telkom's ADSL you still can talk, but you can feel the differences though