My 2 cents worth..
I am not a big downloader (about 110GB per month on average) but I do browse a lot, stream music, YouTube, and play some online games with Xbox Live sometimes, and do a few NZB downloads. I was on Mweb 4Meg Premium Uncapped but downgraded to the Mweb 6Meg Standard Uncapped because it has about 160GB threshold which is enough for me and I sync at 6Megs to the exchange. That said, I have been on leave since 13th December and I have experienced a very good performance everyday at any hour. I have streamed music, had a NZB download occurring and been browsing at the same time without any performance issues. I seems that if you remain "Unthrottled", your experience will remain good.
So my opinion is that if you are a small downloader like myself but want decent experience, Mweb might be a good choice.