They've shown explosion in the preseason, but until Sam Bradford shreds defenses in games that count, I'll remain unconvinced.
He's never completed more than 60% of his passes for a season in his career. I'll wait and see before I believe in all the "downhill" hoopla about their running game too. Kelly's RB's during his three years at Oregon were LaMichael James and Kenjon Barner, both of who went about 5-9, 185 and depended on their speed. The guys Kelly recruited to replace them were the exact same type of back, if not a little smaller, so I'm not sure what to make of his claim that Murray fits his scheme better than McCoy. Philly got a lot of love for their great run blocking in 2014, but I didn't see that at all. It looked like to me that McCoy often made yards where there were none and averaged a whopping 4.2 yards a carry. They get Kelce and Johnson back healthy, but they lose both starting guards, one of who was an All Pro, and replaced them with a couple of journeymen. How can the Eagle OL be better? They let Maclin walk, drafted Agholor and brought in Miles Austin. So, they trade a quality #1 for a rookie and an aging vet who, bless his soul, has never been anything but inconsistent. Matthews had a stellar rookie campaign opposite Maclin, but can he be THE guy? If he can, I think WR could be the strongest position group on the team. Celek and Ertz are part of that, two big, speedy TE's who can catch.
They really upgraded their secondary with Maxwell and Thurmond, and drafted Rowe (who I think was a little overrated). Their inside linebackers will be better too, with the return of Ryans and the addition of Alonso. Benny Logan is an above average NT and, of course, Cox is a beast. Pretty good personnel. But their outside pass rush is a huge question mark with the exit of Trent Cole. Barwin had a great year in 2014, but he'll be getting the double teams now, so it will be up to Graham to step up, and thus far in his career he's been mediocre at best. They will spend more time on the field than any other bunch of defenders in the league, too, which should help their outlook.
My guess is that the offense slides some and the defense gets a little better, but as of right now, I don't buy the preseason hype.