The fitness industry is a cross current of trends, scams, and classicists who stick to tried and true methods. The “experts” are constantly re-evaluating what exercises you should, and shouldn’t do, labeling the “bad” ones as non-functional and contraindicated.
It’s almost always bull. Here’s a great posting from a great fitness educator, about the leg press machine:
http://www.t-nation.com/free_online_article/most_recent/is_the_leg_press_worthless
Fitnessgroan's Blog 
Interesting article. I don’t understand the part about blood pressure. I thought not raising it was a good thing and that taking medications to lower high blood pressure was a good thing. What the following quote says seems to indicate that pushing up the pressure is a good thing.
T
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The researchers found that systolic pressure doubled, and diastolic pressure was on average 2.5 times higher than at rest. This differs from cardio-based exercise, where diastolic pressure barely increases, if at all.
What this means is that there’s minimal to no pressure difference between a systolic and diastolic pressure, meaning blood is being “squeezed” by the blood vessel in between the pressure exerted by the heart and the relative back pressure exerted by the working muscles.
To overcome that resistance, the smooth muscles of the veins have to bust their ass to push harder, effectively making your blood vessels dieseled out way more than the dude who just ran a marathon on the treadmill.
I’m not clear what a full range of motion means for leg presses. I was always told not to fully extend the leg because it be hyper-flexed or some bad thing. Also, I stop the legs coming back when my upper and lower legs are at a 90 degree angle.
T