OS6 is much better than OS5 but it is, however, a memory pig. If you have a newer Blackberry with more RAM, it will probably be fine, but in my case(I have a 9700) I am always running out of memory, the processor is sluggish, and the battery life is depleted greatly. However, I do have a terrible habit of running several programs at once, so if you use the memory sparingly, do one or two tasks at a time, and clean out and refresh your cookies on a regular basis you should be fine

OS 6 seems a little slower but it is so much more intuitive then the previous versions, the only drawback seems to be the browser that due to insufficient memory will not allow for certain pages to be loaded, other then that OS6 is just more fun,