Shape5

My personal suggestion is to release template source in more formats than PSD only.

I can understand why you're using PSD, and it's perfect for you and for customers too if they have certain software suites on their computer

But until you have them, will be hard to customize and/or edit the template design

Consider that these programs are all but cheap (most of the buyers can't afford these expenses, in my opinion) and  using a trial version gives you the chance to customize things until trial expire (and this is unacceptable)

Realeasing the template source under a file format that can be handled with free software will be really a plus (and leaves in customer pocket's the money for renewing their subscription for the next years)

GIMP's (http://www.gimp.org/) native format will be a great choice (cross-platform, open source, etc)
GIMP can already open and modify PSD also, but text will be rendered as bitmap and won't be customizable
Maybe in the future the developers will add support for text interpretation as object

Another great free tool is Inkscape (http://www.inkscape.org/) that works in SVG and last but not least, OpenOffice's Draw (http://www.openoffice.org)with it's OpenDocument format.

I really have no idea of how much work this "cross-release" will take and how could be obtained...