[guitarmantyler]

Certain themes I have downloaded, some from the app world, others that are user made from the forums, are laggy and slow to react to the trackball.

Others like the default apps that are pre installed on the phone have quick reaction times, and no lagging.

Posted from my CrackBerry at wapforums.crackberry.com

[jeffh]

A theme is an application running on your phone. As with any application, there are at least two factors beyond your control that affect performance: the skill of the programmer and the complexity of the operations being performed.

[flashman03]

Yup, and please dont believe that paying for a "premium theme" would be better than a free theme. Sometimes the premium themes are much worse in terms of performance.