Ok, so I've had my 60GB promotional sim in my SGS for the last 2 weeks or so and really don't have any complaints.
I opted to not port my number, so that I still have a back-up sim card for worst case scenarios as I mentioned before.
I've not yet hooked up my dongle to a PC or laptop, so I don't have any feedback in that regard, but for the first two weeks of December, I loan it to a colleague and he said the installation of the software was painless and speeds were great.
I think he'll be leaving Vodacom and getting one of these deals for himself
Downloaded the speedtest.net app a few weeks ago to the phone and speeds to the WA server in Newlands have been constant around the 2Mbps down and 1.5Mbps upload and pings varying between 190 to 350ms.
Just did another test now and I've got 2463kbps down, 1292kbps upload and 139ms ping.
Another test now to Jerusalem show 881kbps down, 78kbps upload and 425ms ping.
Now I browse alot, use apps alot like, Facebook, Twidroyd, MyBB, XDA devlopers, youtube, Gtalk and Gmail.
Youtube vids stream instantly to the phone with no hassles or pauses, under 5 seconds to load and instant play with no buffering.
In the last week I've asked a friend in the UK to setup and FTP server at his house for me and asked him to leave some music and vids on there for me to download.
Downloaded an FTP app: AndFTP for my phone and an unrar app called eFile.
Have been downloading at various times of the day and night and getting speeds do not drop below 100kbps - so I'm chuffed with that
I reckon the downloading from the ftp could be faster, but I'm being held back by his upload speed and whatever other downloads and generic web usage his got running at his place. His got a 24Mb line, so I should be getting more juice

But I'm very happy with what I'm currently getting out of him, the CellC network and my phone.
On the telephony side of things, I load airtime with no hassles, use USSD codes to check my airtime and data balance directly with the SGS.
I do wish that there was an option to go to per second billing.
R1.50 for a 20 second call is a bit hectic.
I don't load anything more that R25 at a time, because I don't really make a lot of calls.
But I think I've recharged at least 3 times in the last week or so.
My calls are always sweet and short most of the time.
I used Skype once thus far for a call.
I was in Sea Point at CallAPizza at around 10pm one night and called my buddy in the UK.
The latency was terrible really, and I couldn't hear him too clearly, though he mentioned he could hear me just fine.