I've levelled up a gym from L9 to 10 today to get my pokemon in. That's my two regular slots back in action. They tend to be fairly static in the term time.
We had spoofer issues a couple of months ago. Suddenly the usual names of trainers L28-32 were cleared out and the team changed to L35 players of themed names like Dishyfella 1, 2 & 3. I saw what I thought was an opportunity to knock down a L3 gym, went into the woods to do it, and Dishyfella aka the invisible man beat me into putting a pokemon in. 
The gyms were also changing at night when it's pitch black in the middle of the woods in the middle of winter.
It is flaming annoying as it prevents legitimate players who grind away putting the time in from accessing the coins, and wastes their resources of revives and potions which makes progress through the game annoying.
A problem I found back in the autumn was that the gyms were jammed at L10 with no change for two months. The level of the players was fairly stagnant and I suspect that they dropped out as some of them haven't reclaimed their positions again. It was frustrating that there wasn't a legitimate way to get them active again.
I can see the gyms from my house, so taking an unhealthy interest in them is very easy 
In other news, the DCs swimming lesson is at a Magmar nest this week.