Is the Demo man's high capacity Scottish Resistance sticky bomb thrower useful in TF2? What tactics does it encourage, and what does it discourage?
The Scottish Resistance is largely a defensive weapon. It allows you guard multiple places all at the same time. Since most capture points have multiple entrances to get into the area, you can sticky up each entrance - and even the capture point itself. If a scout jump through one spot, you can detonate only those bombs, without losing your entire "sticky trap". You can place 14 bombs - instead of the normal 8 - so you have the ability to lock down a huge area.
This does force the demoman to be very aware of a large area. After you blow up one patch of bombs, and laying the next, you still need to watch to see if any more enemies are near your other traps.
There is a longer delay in being able to detonate these bombs after launch. Therefore, it's not as good as a "dueling" weapon. You'll be more reliant on your pipes for that.
I've seen it used with some success (i.e. it killed me) when defending the bomb cart. The demo would shoot some around the current cart position and some more a few meters down the track, so he'd kill both the first wave of enemies attempting to push it, and the second wave.
I haven't seen it successfully used in any other scenario.
The Scottish Resistance makes an excellent defensive weapon for covering multiple entrances. Offensively, it doesn't have the same capability, unless you're also supported by an offensive engineer or the like. Also, use it as an early-warning system by placing your stickies in plain view. The extra capacity allows you to use stickies liberally.
It makes an excellent weapon for camping/covering multiple entrances. Shoot it just above a doorway and when someone walks in, detonate.
Detonates stickybombs near crosshair
Able to destroy enemy stickybombs
+50% max secondary ammo on wearer
+6 max pipebombs out
0.4 sec slower bomb arm time
(Pros/cons taken from TF2 Wikia.)
Another good use of the Scottish resistance is making "backup" traps. Even in areas where there are only a few key choke points, you can lay multiple traps leading towards the objective, so that if someone avoids or survives the initial trap, you've still got a trap behind that one to catch them or finish them off.
You will definitely want to be towards the back of your team line though, regardless of how you use this weapon. The more distance you have between you and the other team, the more time you have to set up the Resistance.