Biospira is hit and miss at best. I have heard stories of it working perfectly and I have heard stories of it actually making the cycle longer. That and other stories of it working for x number of weeks and then the whole system falls apart. I would make sure to test as much if not more often after using it after you add fish to make sure the whole system doesn't crash.
As for the fishless cycle, I am not sure why you could not add a normal bioload to a tank after doing one. I have never heard of any problem doing it and I know people who use the fishless cycle to prepare tanks fpor very large and messy fish like Arrowana and Oscars. If it can prepare a tank for them then it should be able to prepare any tank for our more common and less messy fish. The peope who introduced me to it have done so for many years without any problems.
I swear by it. I did fishless cycles on both of my tanks and I was able to add a full normal bioload without ever seeing any sign of ammonia or nitrites.