I've pretty much given up mileage runs as of the end of last year. It's my view that the overall value of status has decreased, perhaps significantly, because of a number of factors:
1. increases to award levels, meaning the financial value of bonus miles is now less than before
2. reduction/elimination of meal service in FC
3. increased costs for buying upgrades (with cash or miles)
4. increased use of RJs (no more FC)
5. increased use of check-in kiosks (no real benefit to status for waiting in line for check-in)
6. increased risk of airline FF programs going out of business

I value my AAdvantage miles at 1.3 cents each; with other airline programs the figure is somewhat less. Finding mileage runs that generate miles at a cost less than that is possible, but very difficult, especially when you consider airport parking, hotel, etc. Since my MRs are limited to weekends, that makes it even more difficult. By the way, I can't understand people taking vacation time to do MRs! Unless you are taking a vacation, in which case it isn't a MR, that cost would need to be figured into your MR and would surely not make financial sense. In any case, if I am 1 or 2 trips short of reaching Platinum I may do a MR to hit that, but otherwise I won't bother collecting additional miles at a cost higher than I value the miles at.