Going off the top of my head, mainly based on a trip at the end of last month:
Space was down
It used to be a great time-saver until word got out about it, then it became rough. I've often seen it take just as long as the standby line.
Matterhorn was hit-and-miss, but usually not too bad (maybe 10-15 minutes or so). However, I've also had days where it was group after group of 6 people, then 4 people and 2 immediately behind them. Then another group of 2 with 4 behind them. And on and on and on. I feel like this one also varies when there's people trying to use the SRL but clearly wanting to be sat together, and the cast member allows it, and will wait for a group of 4 to put the 2 "SRL" guests in together, pretty much defeating what the SRL is for. Clearly I'm a bit salty about this!
Indy used to be pretty good, but I haven't seen a SRL there on my last few trips. Not sure why.
Smuggler's Run is always an easy SRL. Rarely is there more than 2 people in front of me. The unfortunate part is 90% of the time you get whatever the furthest back-seat position is. But I've had a few instances where people in the group were afraid to pilot, and asked if I wanted to do it. ..... and I've gone early twice and was given my own Falcon, which was fun!
Incredicoaster, like someone else said, can be hit-or-miss as well, but it's generally an easy line to see, so I look at the line before joining it. On especially busy days, people will do the SRL without looking at the actual stand-by time and do themselves a disservice by doing the SRL. I've had a few awkard-ish moments when a parent or child wasn't expecting me to sit by them, but it's pretty rare.
Grizzly I haven't done SRL in quite a while. I've got balance issues along with a joint disease that causes painful swelling, so I use the accessible raft.
I haven't seen SRL at Soarin' lately, but in case it comes back, DON'T DO IT! Okay, so maybe I'm just spoiled. If I go through the regular line or use Lightening Lane, I always wait for Gate B, Row 1, ideally 4-5 people into the row. Obviously, going with SRL, you don't get to pick were you sit, and it seemed like I always was assigned gate A or C, and usually over to the far sides, so the Eifel Tower was bowed *really* badly. The SRL also never seemed to go much faster than the regular line, so you'd still be stuck in the endless hall for what felt like hours (or, maybe 20 minutes on that hard concrete floor).
On the rare times I did SRL on Goofy, it never failed to surprise my seatmate, and boy could it get uncomfy if I was next to someone with long legs, or thick legs where manspreading just kinda has to happen in a car that small, especially when I was Pooh-shaped.
RSR's SRL is so well know that it's almost always a long line. Biggest hint with deciding whether to use it or not-- look at what lane it is (the far left one) and follow that walkway. If you see people at the bridge overpass, you're looking at a wait of 30-45 minutes. I bring a book with me to DL, so a 30+ minute line is 30+ minutes of reading, so I don't necessarily shy away from a long line there.
That's all I can think of at the moment. My mind has gone blank and I'm too lazy to see what other SRLs I missed.
