The Caps would probably be one of the peskier matchups in the east for the Penguins, they always play their hearts out against the Pens. That said, all the Pens need to do is match that effort. They're a much deeper team. I really don't expect Ovie would be stopped, he scored against the Pens even when the Caps were struggling. But the other lines and supporting casts matter, too.
Regarding their chances overall, one thing I have noticed about the Caps each year they contend is their lack of veteran presence (with the exception of occasional guys like Fedorov or Knuble.)
Last year I felt the Pens needed more "grizzlies" -- the core aren't babies by any stretch but I think if they had more vets or characters, they would have been more focused and composed against the Flyers. Not that this is the only thing that was a factor, I know that's not the whole story. But for years (especially late Lidstrom era) people mocked how old Detroit was but they had a ton of grizzlies and always competed well in the playoffs.
For whatever reason, the Caps remind me of the Pens as far as having a good nucleus of talent, only they remind me of the Pens without the pre-Shero additions that put them over the top.