Between them, the file mirrors listed on ftp.html have significant bandwidth available, and it's not like this is some 4GB-per-arch OS for a basic installation, you're talking a couple of hundred MB. Just pick a mirror from the list and download the relevant installation files. If it's too slow, pick another.
Testing a handful of mirrors, even though it's release day, I still see pretty decent speeds: toronto 20Mbit/sec paris 70Mbit/sec zurich 50Mbit/sec london 440Mbit/sec orlando 10Mbit/sec stockholm 40Mbit/sec amsterdam 50Mbit/sec (I'm in the UK so obviously nearby mirrors will do better for me - that is how TCP works - my reported speeds are likely to favour mirrors with IPv6 as I have quite a lot better/faster connectivity that way). Even if there was a problem, bittorrent can only usefully cover the base OS not packages which account for the bulk of transfers, so it would add a lot of complexity and fragility with little benefit.
