Having a synched trusted system with a Blackberry has been a constant struggle for me since I started GTD. I was previously an adherent of the GTD plug-in for Outlook (which relies heavily on Outlook tasks) but the built-in native BB task app just was never built for this. I mostly have ended up ignoring the native BB task app because of this. When mobile I'd taken to emailing myself random actions and then turning them into tasks on my workstation. After a few month experiment with Nozbe, I've moved over to Toodledo, thanks mostly to Proximo's great guidance :-)
Having played around with TaskJot for the last few days, I think I've found a workable mobile system that interacts very well with Toodledo. Adding actions is very straightforward, as are completing and reclassifying actions in a variety of ways. With this setup, I think I finally have a good mobile version of my trusted system.
I'm not religious at all about the my BB, but it's what I have for now, and I remain open to a different mobile device at some future point. But if you are a BB user and you are doing GTD, and of using Toodledo, this is absolutely something worth looking at.
The developers are very attentive and I think you will see quick and continued refinement of their solution. The initial version I downloaded for trial worked well, but when I downloaded an update to take advantage of the "Jot View" (ability for the app to open up in save view), I had connection issues. Within a day they sent me a new version that fixed the issue.