I'm a seriously difficult customer, would recommend in this order with reasons why:
Amazon.com - Responds very quickly, emails are sent constantly to make you aware of your order status, even for the smallest delay. They replace a kindle at the drop of a hat. These guys are the largest online retailer in the world by far, and for a good reason. Not to mention they sell pretty much anything. I buy most of my difficult to find hardware items from them and forward using a forwarding service (postbox-courier).
Takealot.com - The Amazon.com of SA in my opinion. They offer free shipping (sometimes this will be same day), same day shipping, weekend shipping. They give you a call to ask when you want it delivered. Keep you informed VIA calls & SMS. Tracking is excellent. I've had these guys send out a courier Friday at 7pm because I was adamant they said it would be shipped that day. These guys deliver like no other SA company has thus far.
Wootware.co.za - I was pretty difficult with these guys and they came through in the end, reply to emails very quickly, shipping speed is average however (2 days). The only reason I would recommend them is because they did come through on a difficult order for me.
The following shops I've used but their service is pretty average:
Landmarkpc.co.za - Nothing special. I was just another customer and took a long time to ship my order. Don't really get all the fuss over this retailer... I'll be order again from them in a few days. Will come edit my opinion if they seem better.
NGRComputers - Take hours to respond to emails. Slow shipping. Really, with all the options, you pick these guys because you really need to save that extra R40 or because they have an item you can't get elsewhere.
prophecy.co.za - I nearly put these guys in avoid. So many of my friends have had bad experiences with these guys. Their service is also slow and expensive. They were great in the early days but now, just another store.
I've used a lot more than those listed here. All of the rest are pretty fuzzy, meaning the delivery was 2+ days (slow) with average or below average feedback and slow customer service.
Avoid:
Sybaritic.co.za - Have had incidents with this guy before. First motherboard I bought there was DOA. I got a replacement and suddenly it arrived in a sealed box (different from the one I had that was DAO). It also had many extra connectors. I realized at that point I had gotten someone else's DOA or could have been that I got someone else's return. Either way it was dodgy and I had to pay for the back and forth.
Next time I had to do an RMA which I had to go through a lot of sh$t before this guy would actually honour it