The difference are in the features... they added panoramic option (and improved them with later releases) then HDR and now 3d.

Trouble with every software they want to be everything for everyone which never works (for the client) but works well for the corporation who racks in $$$ for each iteration and upgrade.

What I really would like to see is modular software where you purchase only the basic package then add modules as you go along. That was partly the purpose of adobe plug-ins but this is not true anymore.

How many will want to go into solarisation just for the heck of creating one odd picture among thousand that just need minor adjustments?

In 1998(?) I purchased ACDSee 3.1 for $14.00 it is a fast image viewer, minimal editing and enough for my needs at the time.

Guess what? Even now it is adequate for my need (quick sorting/renaming) They have had numerous upgrades since, came out with new titles and so forth. The list price is now about $200.00 Guess how much it would have cost me if I had followed their path as a customer?

(Sorry, ranting here but this is my main gripe with all software and OSes - I am an IT pro).