For our upcoming trip, reserving directly through Disney was less expensive than renting points.
For an identical situation? I find that very hard to believe. For instance, a Value 1 season Value Studio at AKL was $300 per night for 2012 through Disney direct. Point wise the room would have been 9 points mid week, 12 points weekend, or 69 for the whole week. So 7 nights at $300 per night would be $2100. Renting points at the typical going rate of $13 per point should have cost $897. That's a cost savings of almost 60%. Even looking at the Holiday season (Christmas to NYE) is $515 direct vs 16/19 points or $208/$247 to rent. Once again, potentially 60% savings. Maybe I'm missing out on phenomenal discounts, but I don't believe that any widely available discount offered within the last few years has been greater than 40%. A 2BR villa in that same value season was $635 direct vs 25/30 points or $325/$390 to rent.
Now if you were say comparing a moderate resort direct through Disney vs renting points for a 1 BR (to accommodate a typical 4 person family), then yes, going direct could possibly be cheaper than renting points. But you don't get the extra space, no kitchen, etc.
As mentioned, renting points is the basically the same as if you actually owned the timeshare. You don't get daily housekeeping, and the owner needs to make any changes to your reservation in case either of those matter to you.
There is no minimum stay with DVC, either owning or renting through an owner, as it is a points based system. So the owner simply has to have enough points to spend the night, and it's all set. You could in theory spend one night at each DVC resort on property if you wanted.
If you do have a real strong desire to stay in a certain property, don't wait to long. Owners can book 11 months out at the property they own at, and 7 months out a the other properties. So during busy times they can book up fast. For instance trying to get into BW or BC during F&W can be very difficult if you don't own there to book 11 months out. However if you don't mind what resort you stay at, there is the slight chance you could get connected with an owner who has points that will be expiring soon, who will be willing to rent them for less than the going rate.