I too just received a call from Vodacom saying that I'll be credited for each day that the problem is ongoing (so far since 31 March) and this was only with a call to 155 some time back - no letters, e-mails, threats, etc need so I think (at least for me) Vodacom are being pro-active on this issue.
I'm sure though the more feedback that they get regarding this problem from people like us on the forum, the easier it is to try diagnose and rectify the problem, so I'd suggest calling in to 155 with your query, getting a reference number, and updating them on what your experiences have been so far.
Personally for me I'm still experiencing the problem, no more disconnecting, but the downlink stop happens quite often, and I don't think it's hardware related as I am seeing this with both the old 3G card, and the HSDPA card, and infact it's worse on the HSPDA card, but after a couple of seconds the link comes up again.
It also to me seems to be localised to certain areas, at home it's a real pain, but now at the office (a block away from Vodaworld and Siemens) and there's no problem at all?