I have the LaserLyte 5" "quick draw" target, and while I was skeptical at first, I've found that it really does help in some circumstances. The trouble with dry firing is a lack of feedback. The laser helps tremendously with that. One of the first things I learned was that I was failing to hold the gun steady while firing...even if the shot landed where it should, the laser would always sweep across the target. By making sure I followed through, my real shooting became more accurate almost instantly.
The target itself isn't terribly useful just for practicing accuracy. Honestly, just picking an area on a wall, like a switch plate, or a paper plate taped to the wall, will be enough. Even focusing on the front sight, you'll still be able to tell whether the flash landed where it should.
The one place where the target has been useful has been on timed fire. I got an insert for my 9mm that fires the laser when the trigger is pulled, so I can start the timer on the target (counts down from 5) and on the beep, draw and fire from concealment. That's been tremendously helpful for improving speed and accuracy from a draw, which is something almost no range allows these days.
I've even begun using the laser insert at the range, between live fire sessions, to work on accuracy and dry fire between shots. I triples my trigger time but for the same cost of ammo.
So in conclusion I'd say:
Laser cartridge for your gun: absolutely worth it
Laser target: meh...kinda...helpful for timing your shots, otherwise you can get by just by seeing where the dot hits the wall.