Well, things just haven't gone as planned according to DrByte, Zen Cart's head guru. Version 1.5.2 was released in beta last fall and I've been waiting around for the finalization every since.  In the meantime, many hosting companies started upgrading their servers to PHP 5.4. Though 1.5.1 can work on that PHP version but has a few issues, I have been advising waiting to upgrade and suggested moving to a new hosting company in the meantime. This was what I considered to be the safest route.

As it turns out, many started installing the 1.5.2 version even though it was a beta version and not deemed ready for prime time. Today's forum post by DrByte mentions this, http://www.zen-cart.com/showthread.php?213429-Upcoming-versions-1-5-3-and-1-6-0-compatible-with-PHP-5-4-5-5-5-6.

So the Zen Cart core team started treating 1.5.2 as its own version and switched to working on 1.5.3 which is now in the queue for approval by the PCI folks as this is going to be a certified version just like 1.5.0 was. 

1.5.2 and therefore 1.5.3 and all future versions has one major change which requires a change to my servers. I am testing this now on my small server that does not have working Zen Carts on it in order to make sure I don't create any problems on my larger Zen Cart server.

Once I have added that in this week, I can start upgrading sites on my server. I'm offering special pricing to my hosting clients for 1.5.2 and 1.5.3 so please contact me for rates. Upgrading is not required now but will be in the future so the server can be upgraded to the most recent approved version of PHP.

For the average client not on my hosting, upgrading now to 1.5.2 is okay according to DrByte. If you haven't already done that, I really think waiting until 1.5.3 is released is better. That release date is dependent on the PCI certification process – not under the control of the Zen Cart core team but if you haven't upgraded yet, I don't see that waiting should be a problem.