Parallels Version 6 is being release 14th Sept.
Full Version price US$79.99
You can upgrade now directly from the Parallels website for US$49.99
http://usa.novadevelopment.com/EM/2010/parallels/36/P6_0910_…
But until 14th Sept the website Mac Update Promo is selling "upgrade" versions for $US39.99
NOTE: They are actually selling genuine discount versions of Parallels 5, which if sold after August 15th, are eligible for a free upgrade key to version 6, redeemable here… http://www.parallels.com/keyfor6
Reading the guff at Parallels site, it seems to be a worth upgrade from Version 5, and if you can save a further $10… it probably makes it about the right price. $50 upgrade a bit pricey IMO.