Both new users and advanced users will find many important features in 6.15 that make MUDding even better. Also, all of the known bugs in 5.55 were fixed. I'm assuming that you are using zMUD for MUDding because it has the best user interface and the most power and speed compared to any other MUD client available. A new Settings Editor works more like Explorer, and window Docking and layout features give you great control over all of your MUD windows. It also has even more options for customizing how zMUD works.
Text scrolls faster and windows pop up quicker.
Also, with fewer bugs, there is less chance of corrupting your character settings v6.15 has a new database interface to the MUD Connector list, allowing quick and powerful searches for new MUDs to play. The new syntax checker and debugger requires some minor changes to the zMUD scripting language. If you are upgrading from v5.55, you won't have much problem unless you were using unsupported syntax in your scripts. From v4.62 you might have to make a few more changes, adding parenthesis or quotes to things. However, the syntax checker and debugger makes it fairly easy to track down any problems.