Over the weekend, we got a number of reports that Apple appears to have downgraded the SATA controllers in the 13-inch and 15-inch MacBook Pros from 3.0-gigabit to 1.5-gigabit units. Going over the evidence, it looks like they were right.
The issue has been examined at length in the MacRumors forums, where dozens of users are sharing their experiences, benchmarks and varying levels of disappointment. Here are the kinds of numbers they're finding with faster SSDs (excerpted):
Older 13" MBA, 13" MB, 17" MBP (and old versions of 13"/15" MBP):
Sequential READ = 225 MB/sec Sequential WRITE = 180 MB/sec
New 13" MBP, 15" MBP
Sequential READ = 115 MB/sec Sequential WRITE = 95 MB/sec
This sounds terrible: the potential read speeds on the new MacBook Pros have essentially been cut in half. In real-world scenarios, though—particularly Apple-sanctioned real-world scenarios—the speed differences shouldn't matter much; since the MBPs ship HDDs that aren't quite fast enough to max out a 1.5Gb interface, the issue will go unnoticed by most users.
The problem, though, is with upgrades: there are SSDs on the market that can reach and pass the 1.5GB/s threshold, and in the near future they'll become much more common, and cheaper. There's speculation that this could be remedied with a firmware update, but many are saying this is unlikely; after all, reverting to an older firmware wouldn't have saved Apple any money, while reverting to cheaper hardware would have. [MacRumors —Thanks, James, Serrada and Kim!]