It's worse than that... You don't even get 150MB/sec because of overhead and other advances made with SATA II.
Check out these benchmarks for an OCZ Vertex 128GB SSD drive from Macrumors.com
Test: Sequential File Read and Write Throughput
App: HD Tune Pro 3.50
Drive: OCZ Vertex 128GB (MLC)
SATA II: 13" MBA, 13" MB, 17" MBP (and old versions of 13"/15" MBP)
Sequential
READ =
225 MB/sec
Sequential
WRITE =
180 MB/sec
SATA I: new 13" MBP, 15" MBP
Sequential
READ =
115 MB/sec
Sequential
WRITE =
95 MB/sec
The speedup from the SSD's fast random access will still be felt, making the user interface and applications snappier.
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However, the SATA I/SATA150 in the new 13"/15" MB Pro will cause an enormous performance degradation when copying large files or transferring large files to and from external drives --- on the order of losing >50% of your throughput![/COLOR]