D3X!
To answer your original question - whether to move from ADSL.
I avarage about 4,5 down and 1,8 up, with a ping of around 55. All the beforementioned are far better than I ever managed on ADSL. Also, it is far more cost effective than ADSL, provided you only use about 5G a month. I worked out the breakeven point for me would have been about 10G, so it did not factor. Changed from ADSL because of poor quality - my 4 meg line would only sync at 1 meg, frequent downtime, poor Telkom service and above all - cost!
I have to date had very reliable and consistent connection. I run the cell-c modem through a Dovado router, which does a fine job of keeping it connected nicely. I have made a habit though of re-booting at least once a week or so.
I have considered getting an external antenna, even been to Poynting, but then stopped myself, realising I was being greedy and that my connection speeds and reception is actually fine.
In terms of overall performance, it is all about perspective. I had poor ADSL, Vodacom 3G cannot stay connected for more than 10 mins, so the CellC to me is excellent and has provided a great balance between performance and cost. I am in fact considereing buying another 2Gig sim as I have a Vodacom sim in my laptop that will soon run out.
Your baseline experience and requirements might be very different to my own - so it is difficult for you to make a decision based on my review. I would suggest to as a first step see if you have reliable signal and connection. Should be able to see that from your cellphone, provided it has 900 capability.
The down side?
-I will lie if I say I have not had disconnections, but that was very rare.
-Second I will reserve any comment since it is maybe still a low userbase> That said however, I got my stick long before they launched in Gauteng (Oct 2010), and I have not yet seen any mentionable deterioration.
Speed this morning
http://www.speedtest.net/result/1276157211.png