panda- were you going to failure on those high rep sets, or anywhere close? i think that your just supposed to do a few light sets and squeeze to get the blood pumping in there, not exhuast the muscle.
goudy/ursus- how many work sets do you usually do for each muscle, and how frequently do you train each muscle?
the way hst works is you build up every workout till you reach your 15rm then 10rm then 5rm - te reps decrease as the weight increases.
you start the routine by working out your maxes i.e. 15rm, 10rm, and 5rm then reduce the weight by roughly 30+lbs - so say my 15rm was 100lbs, i would take 25lbs off that number and my first workout would be 75lbs for 15reps, the next workout 48 hours later would be 80lbs, and so on adding 5lbs each workout till you reach 105lbs - this would be your new rm at 15. then you change to your low 10rm weight. so if my old 10rm was 120lbs i would drop the weight to 95lbs, then 100, etc etc so that when i reach workout number 6 in that rep range i'd have added 5lbs to it i.e. 125lbs, and then drop to the 5rm weight etc etc
the thing was it workout really really well, you do get bigger, even on low calories, but when you took the strategic deconditioning you would lose any strength gains you made and your cycle would start back at the same weights. also by the the of the cycle you feel like death. Overtraining seriously kicked in with me, i found i was getting weaker over time, colds and flus hit me far far too often. i couldn't even have a few beers without being ill for days.
saying that, it is a very very impressive system.
i also did more sets than 1 for each exercise i.e.
i used to do 1 set for 15's as they killed me.
i did 2 sets of 10's.
i did 2 sets of 5's
i also found it was better to rotate the 15, 10 and 5 weights every day of the week i.e. instead of lifting 15rm weights for 6 workouts in a row, i would do my lightest 15rm workout on monday, on wed i would do my lightest 10 rm, and fri my lightest 5rm, then mon back to the workout 2 of the 15rm weight, etc etc this helped a great deal, and is much better for recovery and strength as you are lifting heavier weight on the fri of every week. however the catch was at the end of the cycle you are hitting failure in all rep ranges all in the same week, and in fact normally hit it the week before often too ( that happened with my modified system and the original).
if you are interested i would certainly try it - it does work, and works well.
if you take gear i imagine it is very very effective

i was my biggest when on that routine, i had 19" arms and hadn't touched gear.
i do plan on going back as my current routine is very similar, only very much focused on the basic compound movements.
also the amount of studies that show no difference between 2 and 3 workout a week made me stick to 2 days a week rather than 3. i do wonder though if proper pre/post workout nutrition would make 3 a week more effective than twice a week. the studies weren't taking pre/post workout nutrition.
just some food for thought.
the hst site is:
http://www.hypertrophy-specific.com/hst_index.htmlit has a good explanation of the system and the science behind its creation if you look.