They have a new downloader which I THINK will continue if the connection is interrupted. I haven't had a problem before...
Paying by credit card, the wait is maybe 1 minute. I literally paid and then started downloading their installer.
I don't think you can use download managers or anything. Gamersgate have their own installer and you will also need to install Microsoft .net 2.0 framework. It's a small pain in the ass to download but I got my first game from Gamersgate about 18 months ago (UFO: Extraterrestrials) and I've had no problems with them over three game downloads (four now). You can even download the game later if you need to.
I know it's sad to pay 'full price' for a download only edition, but for me in Australia it is much cheaper this way. My option was to pay $50 Aus from Gamersgate or about TWICE the price for an import from New Zealand from the US.
It's either that or wait for 1C to get their act together with a boxed edition.
You could be waiting MONTHS.