TaskJot is one of the few (only?) Blackberry apps to sync with an online service. Most of the online services have a web site "optimized" for Blackberry screens but for serious GTD, the web interfaces just don't stack up.
Anyone looking for a GTD app for their Blackberry should go download the free trial and try it out for a while. There are some connectivity issues on some devices with some wireless networks but we're working to try to get BIS-B and make those connections more stable.