Stratum: Interpret integer difficulty values as pdiff (or Ldiff, for scrypt) to avoid losing shares on non-compliant servers
Stratum: If the pool target has changed since the job a work came from, check any shares against the new target too in case it expects retroactive difficulty adjustments
Stratum: If difficulty calculates out to 0.999 to 1, round it up to 1 to avoid something SHA2 hardware cannot handle