1st Experience: About 5 years ago (in my mid-50's) a coworker who is also a bassist told me about BandMix when I mentioned I was thinking about getting into playing in a band again (after a 20 year hiatus). I signed up and before long was contacted by a band looking to replace their bassist who was moving out of state to retire. They were all in their 50's/60's and played Classic Rock, Americana, some Grateful Dead, etc. I learned some of the songs in their list and went to meet them and, essentially, audition. It turned out they were great guys, about the same level of musical skill as me. I joined and spent the next two years with them and had a blast. It was a wonderful experience. Like me, they had demanding professional careers, so we practiced every Saturday night (unless someone was out of town) and gigged every month or two. Any money we made from gigs went into upgrading our sound system. It was so fun, not only to be playing in a band again and stretching my abilities, but also hanging out with the guys. They encouraged me to sing lead vocals on some songs and that was a very positive growing experience. I'm a songwriter and they liked my songs and added some of them to the list, which felt great. After two years I decided to leave the band, to focus on original music by starting a band with my wife (and also I was beginning to have trouble with tinnitus and wanted a lower volume situation). I found my own replacement (via a Facebook group for area bassists) and have remained in touch with all of the guys. During the pandemic, the lead guitarist and I did some jamming together online, just for fun.
While I was in that band I was contacted by a couple of other bands seeking a bassist, but I was happy where I was at and eventually cancelled my BandMix account.
I'm in the Seattle area, so big city and more musicians, but on the other hand it takes forever to get anywhere. What this can mean is that when trying to attract other musicians, even through they might only live 10 or 15 miles away, they might consider that too far because of the traffic. It was an hour drive each way to/from weekly practices with that first band, but I didn't mind. I used the driving time to practice my singing.
2nd Experience: My wife (who is a keyboardist/singer/songwriter) and I decided to start our own band (we met 30+ years ago when playing in a band together) to do our own songs, which we had written over the years. We setup a new account on BandMix and advertised for a drummer/percussionist. Before long we got a response from a guy who had just moved to the area (very near us) to retire after living in Europe for twenty years. He is a great drummer/percussionist and a super nice guy, and he likes our weird songs. We rehearsed with him once a week for a few months and then started booking gigs (coffee shops, breweries, etc.) and getting very positive responses. Then COVID hit and it all ground to a halt. Last night we got back together for our first practice in over a year, and it was wonderful. So we're picking up where we left off. He is retired and has a lot more free time, and loves playing, so he has joined a couple of other bands via BandMix--all older people who practice once a week and gig once a month or so.
So I've had very positive experiences with BandMix. One thing we've never had luck finding on BandMix is a guitarist, but I attribute that to the fact that we're doing original music and it doesn't fit into the typical categories, so it will take a special kind of guitarist (who also doesn't live too far away). But we're content to muddle along as a trio for now.
One thing that frustrates me is when musicians post on BandMix but don't upload any audio or video samples. When I got on BandMix the first time around I dug out some old recordings I had done in bands "back in the day" and uploaded them (with a disclaimer that they were old but at least showed that I could play). In this day of iPhones/Androids there is no excuse for not making some audio or video, even if it's just noodling around or playing along with someone else's recording--enough to give a fair idea of one's skill level and style.
