I have two of them and have never had problems...with anything. I have one that has the perforated holes, and another that is what's called a "tile-in" version: Complaints about the drain not draining fast enough may mean there is some problem with the drain pipe itself, not the drain, because the area of the drain holes or slots in a linear drain typically add up to a lot more than that of a standard drain. Someone who had rusting may have purchased a cheap, non-brandname item. When I was shopping for drains, I found a range of prices from about $100 to $600 for the same size drain. I settled on a mid-range price -- under $300 -- from a well-regarded company: Luxe drains The best prices I have found for this brand are, surprisingly, at HomeDepot.

"when you have a sink or a tub, there is a way for air to escape as water goes down the drain. what about for a stand up shower?" Yes. It's the "vent" part of the DWV plumbing. Do a search for "bathroom plumbing vent" or something similar and you'll find results. There are rules regarding vent pipe diameter, length, and how and where they connect.

Yes, The plate is a cover. The top of the drain is a flange that is held tight (hopefully) against the pan to keep water from seeping through, sandwiching either a gasket or more frequently, plumber's putty), by a large nut on the underside of the pan. The only way you can tell it is not leaking is running water and checking from below. I bought a house last year and had this issue in one of the baths we don't use regularly. Seal wasn't tight so I had to use plumber's putty to stop the rather-significant leak (fortunately it drains onto a rock and flows away).

In general it is very difficult to change structural type of stuff like moving a toilet in a condo. It is simply not the same as doing work in a single family residential home. Beyond it probably being difficult to alter the plumbing in the building for such a change, it is unlikely that you would get permission from the HOA. The roof of the parking structure below is most probably not just a slab the way it might be in a single family home. It would have pipes and electrical wiring since there are no doubt lights in the parking structure and there might be pipes and other structural stuff there. The condo board is not going to sign off on something like this without have something that assures them it can be done without compromising the building. And even if that was possible, obtaining that would be very expensive and I doubt would be worth it just so that you don't see a toilet in a bathroom. Bathrooms HAVE toilets - no surprise. A shower drain is different than a bath drain - even one in a tub/shower combo. I live in a condo (FWIW) and when I remodeled I converted the tub/shower to a walk in shower and the drain had to be changed. I needed to access it from my neighbor's bathroom - luckily he gave me permission. The condo HOA needed to approve the change as well but this modification is much less difficult than moving the location of a toilet - especially in a multi-family residence. There are 122 units in my building - all of them have been remodeled since the building was first constructed and not a singe toilet has ever been moved.