Product review (2 stars): The ANSWER to long drying time.
Many complain about long drying time and lack of heat with this Haier Dryer. After studying the design a bit and tinkering with it's workings, I found the answer, and it relates to the bad design of the dryer: poor placement of the heater element.

And now for the explanation:

The Physics:
This dryer has a PTC heater element, which means that there is no thermostat in the dryer - the element itself regulates the heat output based on it's own internal temperature. If air flows across the element and is thus cooled, it's resistance drops, more current flows and the element outputs more heat energy. If no air flows across the element, the heater will heat up internally, it's resistance increases until little or no current flows, and will output little or no heat energy (the element itself will be hot, but will consume little current and output little energy). To watch this phenomenon, plug the empty dryer into a watt meter and turn the dryer on high. Note the watts consumed - around 1000. Now open the door and stick a pen in the door switch and again turn the dryer on high - it will quickly drop from 1000 watts to around 300. This is because no air is moving across the element (it is flowing through the open door) and the heater regulates itself to produce the same internal temperature, but with little energy consumption and output.

The Bad Design:
The drum spins in a clockwise rotation. The heater is placed at the 8 o'clock position. When the dryer is empty, air is able to move freely across the element, through the inside of the drum, and out the exhaust. If the dryer is lightly filled with clothes, the clothing is rotated up past the element, slightly blocking the air moving across it and reducing it's heat output. If the dryer is heavily loaded, the rotating clothing will be constantly blocking the heater's airflow and you will wind up with very little heat and 4 hour dry times.

If the heater had been placed at the 2 o'clock position, the rotating clothing would "tumble down" by the 12 o'clock position and leave the heater's air space to be free of obstruction.

This problem is compounded by: (a) A faulty door seal - air leaks in through the door opening, and further reduces the air entering through the heater's air port. (b) a weak exhaust fan, unable to move much air.

The Solution:
There is no real solution to this design but it can be mitigated in a few ways:
1. Do not load the dryer more than half full. (the manual says 2/3 full, but I disagree)
2. Make sure your vent is always clear and the lint trap cleaned - this helps airflow.
3. Glue down a bead of silicon caulk around the outer edge of the door to help seal it. (you'll need to remove the door to do this properly)
4. Install a baffle inside the dryer to guide clothes away from the element as they spin past it. (put your DIY cap on)
5. Cut a notch in the door and install a fan to push air through the heater. (do this at your own risk)
6. Modify the exhaust fan belt / pulley to cause the fan to spin faster (do this at your own risk)

Conclusion:
I think the design of this dryer has a fatal flaw which causes it's normal operation to be severely restricted. Consumers should not need to become engineers in order to use a simple and standard household appliance.

UPDATE: I ended up adding a fan booster to the exhaust vent, which greatly increases airflow, and shortens full load drying times to a more reasonable 1 1/2 - 2 hours (vs. 3-4 hours).