To clarify, 1 MB/s is 8 Mbit/s. With the current settings, anyone with 6 Mbit/s should be able to join at the first attempt to complete the challenge, however. We’re still testing, though, and we might also do public tests with different settings.
Note that it will still take a while to even get the chance to do the challenge: Every section will only profile one candidate at a time for five minutes, then accept or reject it, and then profile the next candidate. So if a lot of people are trying to join the network, it will take a long time to get accepted as a candidate. Five minutes later, the vault gets accepted as a node or rejected.
This is a per-section limitation, though, not a per-network limitation: So every five minutes, at most as many nodes can join as the network currently has sections.