After overheads, 1Mbps would still normally get results of between 0.85-0.9Mbps anyways, mine always did. Even 2Mbps syncs at 1.75Mbps, which is about 0.875Mbps when you divide it by 2. So something could still be up on his side.
And no, you cannot be happy with losing "only" 0.15/0.2Mbps, since you're still paying for that bit.
It would depend on the line quality. Generally, we'd see average performance in that range, with lines in areas with better cabling and closer to their respective exchanges performing better. Ultimately every line is a unique case, with individual circumstances. There is no way to give an expectation of throughput on any line.