Compare the kulula.com and SAA Internet booking systems.
In my experience Kulula bookings, and fare lookups are quick and painless. SAA's are frustrating.
I don't know if it's a server-side problem, or because SAA just didn't bother to test their site with the dial-up connections that are used by most home users, but SAA's website is extremely sluggish and difficult to use.
On the other hand, Kulula's site is zippy and intuitive. Booking a trip (or making a fare enquiry) through their site is painless. One-way trips can be booked from the main page (with SAA one has to navigate to another page to book a one-way trip).
Kulula's site is, in my opinion, one of the most user-friendly South African websites. I would guess that the simple interface hides some really deep thinking about usability.
Now if only they could do something about the flight delays...
1time also makes fare enquiries a breeze, while Nationwide, with its multi-stage booking procedure makes determining fares more tricky, although their site is not as sluggish as SAA's.