Sean: why list file sizes in KiB, rather than KB? Because even though hard disk manufacturers have squatted on the traditional descriptions of size like dogs in mangers, hard disks are still naturally sized in 512-byte units. So all file sizes are rounded up to multiples of at least 2^9 - if not more, when one considers clusters of blocks.
I think that's what galls me the most - hard drive manufacturers aren't even using the best units for their products in their keenness to pull a fast one on their customers.
Meanwhile, Sean, have you noticed that you're the only person mounting a strident defence of the new way of doing things - almost to the point of telling anyone over 25 that they're brain-damaged...? Methinks thou dost protest too much.
As for the question of Mbits/s, once upon a time there was a unit that naturally encapsulated the "bits per second" measurement; it was called Baud. I remember 300 baud modems; somewhere around the 14.4 era, Kbaud (which as has correctly been stated, was always a decimal measure, having long predated the era of binary computers) suddenly became Kbps. If one were to refer to "gigabit Ethernet" gigabaud instead, the confusion goes away. (No, it's a complex unit - so is the volt, but nobody talks about joules per coulomb.)
So I suggest that the status quo is just fine:
A megabyte is 2^20 bytes, the natural measurement for memory.
A megabyte per second is the natural measurement for data transfer across parallel buses.
A megabaud is 10^6 bits per second, the natural measurement for data transfer across serial lines.
There. What's the problem? What's ambiguous about it? Why should we change the way things have been done for decades just because hard drive manufacturers are greedy? (They've always been greedy. Remember "unformatted capacity", anyone?)