That really depends on what your requirements are.
We have some PS6010XV's and we have them teired. Current active (write-heavy) data goes on RAID10 15k, reporting stuff goes to RAID6 15k, and archive stuff goes to RAID6 on 7.5k SATA disks.
For example, it's end of financial year tomorrow. So tomorrow the new FY11-12 database will go online on the RAID10 array (well, it's already online, but it will go into production), and the FY10-11 will be moved to the RAID6 data for EOFY reporting. All the reports and invoices that will be generated (approx 150,000 PDF invoices will be generated in the next 48 hours, not to mention tax statements, superannuation summaries, and all the fun things that happen at the end of the financial year) will just go straight to the archive storage.
Dell have very good documentation about suggested configurations, from software and RAID settings to the way to set up your switches and cabling. I remember reading their stuff from 7.30am till about 10.30pm planning the new SAN deployment. I suggest you also do the same, especially with such a massive cash outlay investment.