IFs ands or buts...
My point? There are a growing number of pilots taking liberties with these things. Some of the things I've seen include:
-Flying toward them from what would amount to a base leg heading, then turning to final as much as 4-5 miles back, thereby cutting down the time to fly on final, and possibly compromising the separation ATC is using to squeak a departure out in front of him.
-Coming at the IF from an angle sharper than base leg, making a turn difficult. The FMS solution is to project a fix out to generate a base leg fix. Problem is, they're not telling ATC about it, instead they just request "direct FIXXX" and do it without letting ATC know. If ATC had an aircraft on parallel radar vectors and expected them to fly direct FIXXX, as requested and cleared, it could get ugly.
-Heck, on several occasions I have even seen a pilot flying inbound to ADRET for R29 at CYQM from almost exaclty the opposite direction, meaning he's setting up for the ILS29 from right overhead the runway. One pilot told me about he planned a procedure turn at ADRET. The published PT is related to the QM NDB, which means his own PT was never assessed for obstacle clearance like the published one was.
It seems in the world of RNAV, some pilots just don't think about how they're actions relate to the airspace around them, or to their own goals, for that matter. From a pilot's point of view, it really is easy to tell a box to go directly to FIXXX and let her run. There are no rules published with respect to where and how to use IFs like there are for, say, circling procedures. Having said that, it would be nice to let ATC know what you're doing, if you aren't planning to do what you're cleared for. We do see many pilots requesting direct to fixes for approaches and then telling us they plan to do a visual when they get in closer, even using fixes associated with RNAV approaches they tell us they're not qualified to fly. That's just fine by me, since I know they're setting themselves up and keeping ATC informed. Just something to think about.