Microsoft SQLIO Disk Subsystem Benchmark Tool
http://www.microsoft.com/DOWNLOADS/details.aspx?familyid=9A8B005B-84E4-4F24-8D65-CB53442D9E19&displaylang=en
has been very useful in comparing different disk IO systems. I've seen values between 600 on my desktop PC and 8000 on a SAN, and SQL Server seems to perform in proportion to these benchmarks.
Alan