Well, I just spent some quality time with my cassettes and an Alden 35mm daylight loader, and it's been a success, marred by some mistakes.
I really dig the centre attachment of the film in the cassettes, since it means no more tape, and is very solid while allowing for detachment as you reach the end of the spool (no more rewind!).
On the other hand, what requires care, is the closing of the cassettes in the loader. The two halves have to be very well aligned. To test for it, prepare loading by tying film to the center spool and reassemble the cassette. Close the cassette, then reopen it gently. Place it carefully in the loader, engage the winding lever in the base of the spool, then turn left and right the dedicated knob on the loader. You will see the cassette opening and closing. If it works fine, you can now close the loader, open the light trap of the bulk roll, and start spooling.
When you're finished, close the cassette by turning the dedicated knob in the appropriate direction (you remember it, do you?). Open the trap. If the cassette was not perfectly aligned, you might see the spooled film, and thus have wasted it.
Took me three times to figure it out properly!