Depends on the recans... if they are tested, then they are generally fine 90% of the time. They can show signs of aging when they are on the borderline, which shows up as a bit of blue fogginess in the blacks, a bit more grain. Helps to rate the stock slower just in case.
3-perf only has a few issues, one is that your editor just has to be aware of the timecode/keycode issues for creating the final cut list, and since I'm not an editor, I'm not sure what they are exactly, but since 3-perf is now pretty common, I'm sure it's not a big deal. The other issue is that if you want to shoot tests and project them in a contact print, you have to find a lab with a 3-perf projector.
Since the 3-perf negative is Full Aperture (i.e. Super) and is roughly native 1.78 : 1 (16x9) it means that you use the entire negative for a 16x9 transfer and 16x9 display, and almost all of it for 1.85 images... so hairs in the gate are an issue, you have to keep the gate clean.
Make sure you shoot a framing chart that matches your viewfinder framelines to make sure everything is correct and that the post people know how you are framing the movie. That said, even if you are framing for 1.85, I'd probably just make the dailies 16x9 (1.78) full-frame rather than put a tiny letterbox for 1.85.
Obviously you have less depth of field with 35mm compared to 16mm and smaller formats, so focusing is more critical.
Other than that, in some ways, it's easier to shoot in 35mm than in 16mm -- exposure mistakes are less obvious because you have less grain to worry about. Getting a high-quality image is easier. Film negative has more latitude than any digital camera.
Workflow, roughly what is involved is that you make a cheap telecine transfer just for offline editing purposes, cut and then create an EDL (Edit Decision List)... then you take your camera rolls to the D.I. facility along with your EDL and they scan selects off of the camera roll at 2K or whatever, then conform the scans to match your EDL and create an edited 2K master, which is then color-corrected.
However, the other route is to take an all-HDTV path, transfer your film footage to HD (preferably the highest quality HD tape format, like 10-bit 4:4:4 HDCAM-SR). You'd probably make dubs from those HD tapes down to a lower-rez format for offline editing, create an EDL, and then take your HDCAM-SR tapes and your EDL and do an HD online to create an edited master, then color-correct, etc.
There isn't a big difference in quality between an HDCAM-SR D.I. and a 2K D.I.
