I think it's handy, but it shouldn't be the be-all-end-all draw-it-exactly-like-you-have-the-doll posed thing. It is going to have anatomical issues, it's going to have posing issues, and it's going to have....I guess camera issues? Like it doesn't help if you kinda wanna fish-eye a shot is what I mean. But it is a dang handy tool for getting started.
The rough sketch phase is the thing I have the hardest time with in my drawing and using 3D models reaaaaaally helps me avoid the "that is not an arm that is a broken mass of flesh" problems in the rough stages. I've started using it in some more recent work just because I keep trying these difficult angles and poses xD;
From my current WIP:


I changed up the posing for the right arm in the sketch because I wanted more of the arm+hand in the camera. Also realized I didn't angle his shoulders nearly enough. This is just a traceover so I have an idea of where to go from here, like I definitely need to redo his facial structure pretty much 80%, the hand is pretty derped, right side of chest also derped.........there's a lot of work still to go...but it's a much better start than if I had free-handed it ;w;
Another example where I made a really lousy attempt at freehanding a difficult angle first. Left is free-hand (and honestly pretty rushed--I like to think had I put in more effort it might've been much better...), right is the final inking after I had a go at it with a 3D model (don't have the sketch on hand but oh well):


The 3D model I used was way too bulky for this character so I had to trim it down pretty significantly but I think it came out pretty good and a hell of a lot better than my freehand attempt. It's certainly no replacement for actually knowing anatomy and perspective, but in my case I find it a really handy tool to help compensate for my failings.
Edit: Okay I feel really silly that this didn't occur to me earlier, but 3d modeling would probably also be good help for shadow placement if you can manipulate the light source 8V Further investigation required.