I'm going tell you this and I know most people will not be to happy about it ... I too have used HST for quit sometime. I've done 3 full cycles and 1 extended cycle. I did nothing but lose lose lose lose the intire time I was on the basic HST routine. "YOU HAVE TO PERSONALIZE IT!"
For instance ... I through rep count out the window. I do use my 10Rm and 5RM loads ... but instead of only performing 10 and 5 reps ... I do as many reps as I possible can. Sometimes its only 10 reps with my 5rep loads and sometimes it 20reps+. Obviously I'm using my old/previous RMaxes, and when I start over I will have to recalculate everythhing, but my point is I have been training dang near to failure ... AND I"M GROWING! Training to subfailure didnt work for me. So I switched it up.
Also, I dont SD anymore ... screw the SD. Everytime I SD i would lose 5lbs to 10lbs. I was always gaining, then losing ... just to gain back what I lost next cycle. I was getting no where. Instead, I "cruz." When its time to take a break or I see a slow in gains, I step back a little bit, dropping load just slightly and cruz for a couple weeks (4 to 6 weeks). This is not a time when one should focuse on gaining, but simply maintaining.
I found keeping a log with me at all times and recording every lift, load, and rep helps as well. The follwing workout I try to either increase load or increase rep by at least 2. If I cant increase load, I try to increase the number of reps - and vise versa. The log really helps me keep track of where I stand. It helps me from taking those steps backwards ... which is what I was doing with HST (2 steps forward, seemingly 3 steps backward).
So although I still impliment HST principles into my routine, It is completely customized for my needs. I like to think of it as a mix between DC and HST, which are kinda similar routines anyway.
My routine is a 2on/1off/2on/2off upper/lower split. I workout 4 days a week - each muscle group 2x a week with the exception of arms which are worked both directly and indirectly. The routine is Monday/Thursday: Chest, Back, Traps, light shoudler work. Tuesday/Friday: Legs, Arms, & whatever I missed for shoulders during the previous day. The volume is a little higher than most HST routines, and frequency a little lower, but it works for me. Even though assisted, I've made phenominal gains this round.
Find out what works for you!!!