I cannot play until tomorrow late late late. Dammit, I won't have a chance until there's 50 left. But the Engy update is upcoming.
As for the new shotgun, I was half right. It does reward accuraccy more by having a smaller clip. The smaller clip size also limits the crit potential, meaning that you're a lot like the Scout on the front lines; able to pack a crazy powerful punch but your speed and health are still a liability to get you killed.
Overall, it encourages firing with your sentry, and not dying with your nest. If your sentry dies while you're away, you can come in and do the work of two or three guys. This also means that you can better defend the point when your entire team runs off and leaves you alone and unsupported.
If I can get my accurraccy up (My foray into Soldier and the every constant Medic play has reduced my shotgun and flaregun accuraccy by a ton, which is a bit annoying) I could see myself maining this shotgun. You can kill most classes in three nicely aimed shotgun shots, after which point you either want to switch to pistol while backing away, or switch to wrench and charge them.
Edit: There is also potential for an aggressive strategy where you kill a few people, blow up the sentry, then quickly rebuild it. But, unless you have to move the sentry anyway, this strategy will be very risky without at least one other person backing you up, as you never know who will sneak up behind you in the 5 seconds it takes to speed build a new sentry.
Also, with this weapon, I highly doubt we'll get any weapon that speed builds a sentry without a more massive drawback compared to the "no upgrading" as hoped for with the PDQ. It's waaaaaaay too exploitable, especially on pubs. Still, without a PDQ, you won't be able to roll out with the other classes very well still.
Second Edit: Also, someone should make a post in the Gaming forum about this new update. It can be someone who will actually remember to link to this thread in the first post, and will listen to us and take suggestions to update it to look spiffy. We can also wait until Thursday, but the longer one waits...