These are just my opinions:
According to the speedsolving wiki, the steps of heise are:
The first two steps are creating F2L minus one pair + edge orientation. The Heise approach to this seems a little odd for speedsolving purposes and looks to me possibly more suited to a slower solve or FMC attempts. I think something a bit simpler like
- Build a 2x2x2
- Build a 2x2x3
- Build F2L minus one pair while simultaneously orienting the edges
might be necessary to make the method reasonable for speedsolving while mostly remaining in the spirit of the original proposal. That said, I think the ZZ or Petrus approach to getting to EOF2L-1 might just be better.
The first part of step 3: create two corner-edge pairs is usually not too bad. The second part: solve all of the edges and two corners is often not very obvious. It is very easy to create a situation where you have solved the edges and two corners, except two edges are swapped. When this happens, the only way to solve the edges is using something like a J perm (because to swap two edges you also need to swap two corners as well), which is of course a lot of extra moves. To avoid situations like this, you often will need to solve the two corners and edges in a less intuitive way. While many of the techniques on
Ryan's website are effective for avoiding these situations, it would not be good enough to have to figure these things out during a speedsolve. In my opinion you would probably have to make a list of almost all the possible configurations (up to some form of symmetry) you can get at this step and determine the intuitive or non-intuitive solution (many of the intuitive solutions are awkward to fingertrick) you intend to use for each case beforehand.
When you get to the final step, the 3-cycle, the fastest way is of course to use speed optimized commutators from top 3BLD solvers, as commutators that you come up on the fly are likely to be slow. There is probably no good way to avoid the worst case: 3 twisted corners, which requires two commutators instead of one to solve.
So I basically think it would be a very weird method for speedsolving. I would guess that it's probably almost impossible to beat plain OLL/PLL combined with a fast turning speed with the Heise approach to EOLSLL - I just don't think the movecount can be low enough to compensate for the increased difficulty of recognition.
A lot of the problems above are solved by having more time and being able to go back on moves, which is why Heise is a useful method for FMC. Using Heise for speedsolving feels like forcing a method into an application it was not designed for, and for which more practical speedsolving approaches exist for achieving the goals of each of Heise's steps.