I have a DIY jig made from Tufnol which does the same job as a track, and does not need to be set-back from the cut line as you do if just using a straight edge.
Been there, done that. Your straight edge still won't allow you to make splinter-free cuts in melamine or laminate faced MDF, or delicate/splintery veneer-faced boards. And it still needs to be clamped in place which can mark some materials
Even with a straight edge, once you know the allowance for the saw plate witdth, its not really a big time issue in setting it up.
That depends on how much accuracy and time are factors. With a track you don't need to mark the cut line - just put a tick mark at each end of the cut, line the rail up and cut. Start to do any volume of cuts, such as maybe the 50+ cuts you might well need to make to put in store room shelving in a restaurant, or the many cuts needed to put in multiple pipe boxings in an old folks home, for example, and the time saving, repeatability and accuracy become significant advantages.... I've had this particular circular argument/discussion with many, many joiners over the last 20 years (especially when they were told the price of the kit). What's interesting is that they were convinced they are right
at the time - but when I've run into them again on another job 5 or 6 or more years later (or more than 10 years as in one case last summer) it's remarkable how many of them have caved-in and bought themselves a plunge saw, rails and vacuum. What Gossamer says above is very true,
"I now think of a circular saw as a 'construction' tool, for anything indoors like kitchens or joinery etc a tracksaw is the way to go....."
So my thinking is that a circular saw is much more versitile to have in the first place, will do the extraction just as well and can be used with a jig or straight edge for accuracy, and so still fail to see the benefit unless you only ever cut sheets all day long and have no other use for a circular saw.
OK. I'll admit to having a cordless 18 volt rip saw (a Makita DHS680 these days) for 8 or 9 years now and it gets used a lot. But the plunge/rail saw and the cordless rip saw aren't mutually exclusive - they actually compliment each other rather well. But then I do cut a heck of a lot of sheet material cutting (flooring, patress, exterior cladding, shelving, boxing, worktops, counter units, etc) as well more than a few less usual things (doors, window boards, soffits, fascias, cement board, etc) with a track saw.
Saying that the extraction is just as good highlights to me that you've probably never used a professional plunge/rail saw in anger. The difference is very great. The only conventional saw that I've used which can get close to the Festool or Makita plunge saws in terms of dust extraction was the
Makita 5017RKB - a saw specifically designed for cutting extremely dusty products like cement board
I see more and more people talk about tracks as a "must have" tool, but I still can't see why, and think its just all hype.
But I don't think you've never used one, so how can you tell? I don't think it's a "must have" tool for every joiner, but in the interior fit-out trade where speed and accuracy are a must they really are extremely useful. Same goes for kitchen/bedroom/bathroom fitting, etc