No MS for me. I have bought some no fee GCs to places we regularly shop at in order to accelerate spend to meet bonus deadlines but that is all. Being that I have only been at this a little over a year, there are many sign up bonus options still open to me. When those become scarce, I'll consider MS to supplement.
I do not travel much for work these days so really no opportunity for elite status by adding MRs or mattress runs but I totally understand why someone would if they are close to the next level. I did do a mattress run once at a cheap local hotel in order to complete a promo and get a free night that we could use somewhere much better for a planned trip. Saved us about $200 so worth the minimal hassle.