No. You can add programs, but they must be written for GEOS. Generic DOS programs won't work.
<<Is it just dos based, or will it load Windows versions?>>
It's DOS based, but the GUI used is GEOS not Windows. It will not run Windows or Windows software.
<<Is it upgradable when a new program comes along?>>
More or less. You can't remove what's in ROM, but you can add programs.
<<Does OG have the capabiltiy to take a note and transfer it in to a contact managment program or into a todo list?>>
Yes, but you need to purchase commercial software for this.
<<Any thoughts on the OG as a whole, is it worth it, or is there something better out there for my needs?>>
I purchased one for pretty much the same reason: to replace my day planner. I was very successful for about 3 weeks. I ran into two "problems":
1. The battery life was unacceptable to me. The cost in batteries over 1 year was far more than the refill for my day planner. The only way I could get around this was to use rechargeables, which would have added battery management to my daily tasks.
2. I would have to spend as much as I paid for the OmniGo for add-ons to get it up to the point where I could really use it to replace my day planner.
Don't get me wrong. I'm happy with my OmniGo. For what I paid for it, I got plenty. But as a day planner replacement, it has a LONG way to go.