I am a user of Spark and is the best “Open Source XMPP client”, but like all open source softwares have some unfinished details, this details corrected will make Spark an better xmpp Client: (please frogive my english)
1-> Spark client is too silent, it have sounds events, but they have to be activaded manualy; this must be fixed, the sounds should be activated by default and more dinamics sound, they have too short duration.
2-> The bell command shuld have sound it it should move the local and remote window (this will give a better sentation of comunication)
3-> Spark do not recieve rich text format( text in colors, etc. ), the user should have the option to change his text format in the chat window
4-> When a user recieve a message this apears directly in the front window, this give zero privacity when you recieve a private message and you are with people in the PC, this should be fixed too, the ROAR sistem is disabled by default, and it sucks. In Pandion apears a notification in a little box at the right corner
5-> The auto start of the spark is by defauld disabled, this must be changed with an option on the main conection window