You have quite a few picks of ISPs for the IS backbone:
Plugg (IS's consumer arm) - star rating applies, direct line of support to IS techs
Web Africa - star rating applies on home uncapped, business uncapped uses different model, capped has loads of midnight data
Connection *(by Incredible Connection) - star rating applies
VOX/Atlantic - only their uncapped accounts run on the IS backbone, capped on their on backbone, has setup fee, star rating applies
Open Web - they say star rating doesn't apply, who knows with all the lies and shared accounts they came up with, dodgy isp
ITNT - I don't know whether they do uncapped, but they do capped on IS network
Imagine - small isp, support is hit and miss, they do resell IS accounts however
You will see I grouped the above. The 1st set of ISPs are ones I would choose from. The second set I would avoid or is just too unknown to me.
The biggest problem with IS uncapped accounts, is that you have to contend with the star rating system.
5 stars = unshaped
4 stars = shaped, you hit this really fast
3 stars = shaped more, downloads slow down quite a bit here
2 stars = very shaped, don't try downloads, streaming and gaming is affected too now, browsing and email should work
1 star = abuser category or some such, you can expect 0 access during business hours, or at best 56k dial-up speeds. On the more premium accounts however you can get faster speeds after hours, although you should get full download speed midnight to 6am.
So that makes the Web Africa business accounts stand out.
What you can probably expect from the star rated accounts is, you will get similar usage out of them as a capped account at the same price, just slower than the capped account. Then after that you will have super slow access, just to say you are not capped, to stay true to the uncapped account type, but really it is almost as bad as capped.