Sure you can learn a lot on DP but the real challenge is taking action and implement some methods/techniques. 99% of people fail because they are not persistent.
Just don't fall into the newbie trap thinking that you will make $100,000 your first month because you won't. Unless you are very very very lucky.
No offence, but if you are going to tell us how you make $3500 every day, then yes, this is a great place to sell your goods. It's good for services too..
B/S/T section always buzy. Coming together, sharing together, working together, succeeding together. Teamwork divides the task and doubles the success.
DP is good only for people who are learning adsense.. aside from that, I don't see any serious useful topics...
Buy Sell or Trade. The huge sub forum - if we can call it that way - of DP where people buy and sell websites, traffic, templates, and trade services like web design, codding, SEO, submissions, content creation etc. I learned almost everything I know now by working there... Good luck!