Kevin,
Basically, you go to your phone's app store and download myVegas. Start playing their slots and you earn what they call LPs or loyalty points for time played. You redeem the loyalty points for comps at MGM properties. If you just play with the free coins they give you, the available comps they show you aren't going to be that good. Likely, you will get guaranteed room rates or 25% off room rates at MGM properties. You might get one-night free at the Excaliber or Luxor. However, if you spend just a little, your offers will improve.
I spent around $120 in-app over the course of the last 3 months. My room offers are currently topped out at two free nights at the Bellagio or Aria but I can book any lower rung MGM casino. For example, the Mirage and Mandalay Bay are considered the next tier down. I booked the Mirage for 150k in loyalty points. Staying at the Bellagio for two nights would have been 225k in loyalty points. Staying at the Excaliber for two nights would have been 30k. Generally, the more expensive the property, the more loyalty points it is going to take to get the comp. Most weekdays are open for use of the comp and some weekends are as well. I was able to get a Friday night comped but not a Saturday. If I waited, I could have booked a full comped weekend (Fri & Sat) in Oct, Sept or Nov. The weekend nights vary depending on how full the property expects to be and your level of play. For example, I could have redeemed a Fri and Sat night at Mandalay Bay that same weekend whereas I could only get a Fri night at the Mirage.
You can use the comped rooms once every 30 days. Right now I have enough LPs left over to book the same trip over and never have to spend another penny on the game. So for about $120, I got around $1,500 worth of comps.
You can also download the myKonami app and the Pop Slots app as all three apps share loyalty points. If you do all three, you can earn 3 times the loyalty points per day. I tend to stick with MyVegas, but I play a little on the myKonami app too. In the myKonami app you can use your LPs for $25 in free play comps at various MGM properties. It takes me roughly an hour of play a day to max out the daily LP cap on My Vegas. Since I am the first one to arrive at work, I usually load up the app on my phone, pick a game and select auto spin so I don't have to mind my phone. It really is painless. By the time everybody else comes in, I am maxed out for the day.
Given how much cheaper it is to earn the comps in these games vs what it would take to get those offers with casino-play, it is a no-brainer. The last time I played at an MGM Casino was 10 years ago at the Beau Rivage in Biloxi. I put $40 in a VP machine and cursed myself for playing the poor paytable games when I lost the $40 in 30 minutes and didn't even get a free drink out of it. I haven't gambled at an MGM property since. (the exception being live poker tournaments) It is kind of unbelievable they are showering me with free weekend rooms at their high-tier properties for playing their slot app.
Hell, with airfares under $100 RT, and free weekend rooms at MGM properties, I can afford to go to Vegas 4-5 times a year. Since I work 4 10s with every Fri, Sat and Sun off, I won't even have to burn my vacation time.