If there's a downside to TextPad 4.0, it's that with so many changes there are several items you'll need to watch out for when upgrading from earlier versions of TextPad.
First, while v4.0 is a free upgrade for users who registered on or after 1/1/98, you will need to fill out an upgrade request form and enter your new registration information in TextPad 4.0 in order to register the new release. Users who registered before 1/1/98 will need to pay $10 in order to upgrade their registered version to v4.0 (the regular price for TextPad is $27).
Second, the addition of new document classes that allow specific types of files to have their own document properties such as font settings, syntax highlighting, print settings, and tab stops has resulted in the document preferences system being completely redesigned. There are many advantages to the new system, but as a result of the changes no user preferences are automatically transferred when upgrading from an earlier version of TextPad. Properties such as font and print settings must now be defined for each document class by accessing the properties page on the Preferences menu.
Another change to take into consideration involves the new workspaces feature. Multiple workspaces allow you to preserve the state of the documents you are working on by saving these settings under a named workspace. Again, there are numerous advantages to using this feature, but as a result of its addition, the single 'Warm Start' workspace of TextPad 3.x is no longer available in the new release. To achieve a similar state in v4.0 you will need to name and save a default workspace and then select the 'Reload last workspace at startup' option from the Preferences menu.
Finally, the spell check engine in v4.0 is much more powerful than earlier engines, but at the same time it is incompatible with the older engines. Any custom dictionaries or additions to the standard dictionary made with an earlier release of TextPad will not carry over in the new version.
While there are a few additional minor items to be aware of -- such as changes to the method of switching block selection mode on and off and a new, separate command for running Java Applets -- these are the major items to take into account when upgrading to version 4.0.