I have a lot of experience with this. It seems to vary from benzo to benzo, and like others have pointed out, there is no real rush and has a very high oral bioavailability, while most of them have a low intranasal bioavailability. The science behind this is proven and widely accepted.
Now, I will report my findings. I have found that while it doesn't provide an extreme effect instantly like other drugs, it does have a somewhat instant effect. Especially pressed bars, and I also found what doesn't hit you then, does hit you later. Once you put something inside of your body, it can not be un-taken as we all know, and it will hit your system eventually. I think its wasteful, but I still do it because I enjoy railing. If you are low, definitely avoid this. If you want to rail something and have some to spare, its not any worse than snorting anything else.