My experience is that my Gold (Power) account performs
significantly better during office hours than the Gamer's King account that I was on. On Gamer's King, I couldn't do much of anything during office hours on most days.
I think the frustration that became apparent in January was probably exacerbated by the test OW ran in December to measure demand at the higher connection speeds we'd been bumped to by Telkom. Having an all-you-can-eat line performing at double your usual speed (I was on a 2 Meg line, bumped up to 4 Meg) all day long was internet bliss. But, as MrBEEP said, it was unsustainable given the demand they measured.
During January, I had issues all round with my DSL (kicked off initially by me capping the routing account I had due to the above mentioned test - sorry OW

). I lodged tickets and received good, patient support from OW. I was issued with new routing accounts, which performed well at times and then borked at others. Given the many variables in the equation, it was difficult for me to identify whether the issue was ISP-related (shaping, contention) or the DSL service.
So, to remove contention from the equation, I moved to a Gold (Power) trial account, with the assistance of MrBEEP, as this account has a lower contention ratio than Gamer's King. Daytime performance was (and is) stellar. So at least I now knew that contention was part of the issue I was experiencing. To be fair, I was paying a very low price for an uncapped service, so logically I was contending with more people for the same bandwidth.
I signed up for a 4 Meg Gold (Power) account and it has performed admirably. However, Telkom's exchange has not. I discovered that the intermittent performance of the connection was still there. OW was not the reason for the intermittent performance of my account. You can see in my last post that I've had to contend with wildly variable pings on the second hop (us to 2500ms…). I logged faults with Telkom and escalated them yesterday. Late last night or early this morning, something changed. My line is stable and my pings are as expected. Long may it last.
What I've learnt through this process is that the ISP is the front line in terms of DSL issues and, as they are more accessible than Telkom, they take the "heat" for all Internet connectivity woes, whether they are the cause or not. I think there's also the issue of user expectation and at some point we as consumers have to accept that this is a business. Unless we want to be complicit in grinding our ISPs into insolvency, we have to accept that we need to pay for the level of service that we expect. It is expense, but we do have a monopoly - and those monopoly costs are the overwhelming majority of our internet connection costs.
There are of course anomalies and performance issues from time to time, and my experience has been that OW deals with them professionally and attempts to do so with minimum impact to their customers (although even this - namely the issuing of new routing accounts - is treated with extreme suspicion by their clients).
Although I'm happy with the performance of my Gold (Power) Uncapped account, I believe that Capped is the best option for users that require high levels of performance 24/7. They will just have to be responsible and not attempt to download the whole internet every month. (Last bit said slightly tongue-in-cheek)
PS: Here's my latest speedtest, taken a few minutes ago via ssh:
speedtest_cli.py
Retrieving speedtest.net configuration...
Retrieving speedtest.net server list...
Testing from Internet Solutions (196.210.130.93)...
Selecting best server based on ping...
Hosted by Telkom SA (SAIX) (Durban) [16.20 km]: 33.061 ms
Testing download speed........................................
Download: 3.32 Mbit/s
Testing upload speed..................................................
Upload: 0.35 Mbit/s