Picture editors aren't going to edit the location dialogue very much. On occasion they might create a little bit of fill to smooth out a transition, but it will be improperly placed and often loopy sounding. You'll also hear constant squaring off of the audio between shots. Also, depending on the location sound recordist, the picture editor might only work with one of several available tracks of audio. Nowadays it's not entirely uncommon for production sound mixers to create a polywave file with isolated lavs, boom(s), plant mics, and also a standard lav mix. This is where your OMF/AAF comes into play.
@C3Sound Generally speaking, you actually don't want to be splitting by character. Splitting by shot number/angle works better for the mixer as overall they are processing to reduce the overall noise of a scene. The exception is in documentary. As far as fill goes, it's also good to avoid creating separate fill tracks. Fill is present underneath the dialogue, and you fill out between, before and after the modulation.
PFX (any kind of sound effect captured during filming aside from footsteps, cloth movement) should be split off but then fill should be placed where the PFX used to be in the dialogue track. Most of the time when you do PFX they will be some sort of percussive sound, a cup down, a hammer, something like that. You want to cut and use fades to eliminate both the room sound and the reverb as much as possible. This stuff, if used by the FX mixer, will be processed later. You eliminate the room sound because of the back fill you've created. If fill was left in there, suddenly when the PFX happened the noise floor would double.
The reason we mostly split off the percussive sounding things is they make the multi-band expanders pump undesirably at the mix stage. That, and they will be part of the M&E. Movement, though, is considered part of the "life" of the dialogue track and will generally be covered/sweetened with Foley for the M&E.