They can be good. It's just that my needs and thoughts have changed somewhat.
I think they are good if you are going to do a large quantity of cuttings and are able to leave them in the bags until it's time to put them outside. The main advantage of the small bag approach is allowing some root and top growth while keeping it compact and being able to fit a bunch in a small space. In my climate most of the successful cuttings really will need to be put in a 32 oz container or 1 gallon pot before I'm able to put them outside, so I have to plan for enough space to handle 1 gallon pots. So the compactness thing doesn't help me that much, since they all outgrow that initial compact space and then where would I put them?
Also, I already have as many trees as I can handle so I really limited the number of cuttings I started this year. Another reason the compactness wasn't as big a deal.
Another issue is that in the past I've had trouble with over- and under- watering, or both at the same time (dry top and soggy bottom). Frankly it's a hassle to get it right and requires a lot of attention. So instead this year and last I put them in sphagnum moss in the beginning and then put them in 32 oz deli containers when they started sending roots. Sphagnum moss is more idiot proof and I can ignore them for 1 or 2 weeks and feel confident they will be fine when I get to them.
I used to think that one of the main advantages of the baggie approach was that you wouldn't break tender roots like sometimes happens when moving from sphagnum to cup. But now I don't think that's a big deal. If you break a couple roots, that's not likely to doom the cutting. Over watering is much more likely to kill a cutting than breaking a couple roots. And a 32 oz container is just about right so that when April/May hits, they are ready for a 1 or 2 gallon pot. Then I put them outside.
Also when using the baggies I was never that great at cutting the bags and sliding the cuttings out. It's actually worse with the 32 oz containers because the plastic is thick and somewhat rigid. Have to use a knife to sort of convince them to come out sometimes. But by this time they have a very strong root system and there are enough tough roots that it doesn't matter if you nick a few.
I would use them again if I were doing a very large quantity of cuttings, or if I lived where winter was shorter. But I don't foresee either of those things happening any time soon.