Not sure if this is a good idea or not but I had vague thoughts that perhaps a user could be allowed to close their own topic once they'd received a satisfactory answer? This comes out of me scanning the 'Todays topics' and constantly running across topics that have already been well answered (I'd like to focus on the ones that are still unresolved).
1.) Major pro - Able to drill down to topics where assistance is still required
2.) Major con - User might be happy with answer, but extra value and/or corrections could be posted...
Alternative could be to perhaps somehow flag a topic as "Original poster is happy?"
Feel free to tar and feather me if this is inherently not a great idea
The OP could always edit their post, and change the subject to start with "[SOLVED]", or something like that. Personally, I dislike that -- just because the original poster is happy with the answer still doesn't mean the answer is right.