Advantages and Drawbacks
Split supersymmetry allows gauge coupling unification as supersymmetry does, because the particles which have masses way beyond the TeV scale play no major role in the unification. These particles are the gravitino - which has a small coupling (of order of the gravitational interaction) to the other particles, and the scalar partners to the standard model fermions - namely, squarks and sleptons. The latter move the beta-functions of all gauge couplings together, and do not influence their unification, because in the grand unification theory they form a full SU(5) multiplet, just like a complete generation of particles.
Split supersymmetry also solves the gravitino cosmological problem, because the gravitino mass is much higher than TeV.
The upper bounds on proton decay rate can also be satisfied because the squarks are very heavy as well.
On the other hand, unlike conventional supersymmetry, split supersymmetry does not solve the hierarchy problem which has been a primary motivation for proposals for new physics beyond the Standard Model since 1979. One proposal is that the hierarchy problem is "solved" by assuming fine-tuning due to anthropic reasons.
Read more about this topic: Split Supersymmetry
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