I've had the boc-loc HST rulers for over a year now and, yes, they are fantastic!!! You really don't have to buy the 2.5 inch and 4.5 inch rulers. The 6.5 is the better option because it is larger, it is easier to hold down while you trim (and keep your hand out of the way). So, don't feel you need to purchase the entire 3 HST ruler set.
The flying geese rulers are very much worth the money as they trim the blocks exactly each time. I have a number of other flying geese rulers and it was a pain to have to visually line up the roof peak of my block with the lines on the ruler. Most of the flying geese rulers have thick lines so you have to be consistent with where you place the ruler over your block to trim. Also, I found that my Eleanor Burns flying geese rulers were not accurately cut and 2 of the 3 from the set I purchased several years ago were almost 1/8 inch short. I ended up with a bunch of flying geese that were 2 1/2 by 4 3/8 inches.