As people have acquired Windows Mobile 5.0 devices and upgrades, many of them have noticed that these devices are a bit slower than previous Pocket PCs.

Until now, most people have chalked this up to this operating system's switch from using RAM for long-term storage to using Flash ROM for this task. Accessing Flash ROM is inherently slower than RAM.

But a recent posting on the Windows Mobile Team Blog by Mike Calligaro says it is a bit more complicated than this.

http://blogs.msdn.com/windowsmobile/archive/2006/03/16/552996.aspx
via http://www.brighthand.com/default.asp?newsID=12164

Why Persistent Storage is a Good Thing: http://blogs.msdn.com/windowsmobile/archive/2005/07/14/438991.aspx