My nickel:
1. The new timberlines do look very nice. I've thought about adding an induction side burner to my Ironwood 885 and still may some day but for now I'm lazy.
2. I don't think the 780 would be enough. I routinely use a lot of my 885 just cooking for small groups and when smoking bacon the real estate is very helpful.
3. One concern with the Timerblines, they may be too well insulated for their own good for warm weather cooking. You need some inefficiency to cause the grill to use fuel and produce, well, fire/smoke. The Ironwood is only partially insulted and still is pretty stingy on fuel during the summer months. I'd at least way for a few reviews and see how some actual cooks do on these rigs.
4. I love my Ironwood 885. Would I also like a stick burner? Yes. How about a kamado-style charcoal rig? Absolutely. But today I got up at 7, fired up the Traeger while I got Andrew ready for basketball camp, threw on a small pork shoulder and went to the office. I checked temps while I worked for a few hours, picked up the kids and came home. I actually looked in on things and they were still cruising nicely so I wrapped the butt, and left it. My parents arrived a few hours later, I checked on things via my phone, saw the pork wasn't coming up to temp fast enough so I bumped the cook up 25 degrees without leaving my chair. Just an hour later my phone let me know that the pork had reached temp and I went and took it off. That's pretty damn convenient and the food produced is easily as good or better than most BBQ I can buy locally. I'm sure there's better out there, but I'm also sure I'd have to drive an hour or more to find it.
5. Coming from an actual stick burner you might need to temper expectations a little. The flavor will be different. Whether you think it's better or worse is impossible to predict but the fires are radically different between the two types of smokers and the food produced will at least be a little different, but unlikely to be radically different.