I agree O'Hara is unbeatable in the vocal ability and detail in her acting. She was tremendous and I don't think she got enough credit for it at the time because Clark was such a powerhouse. It's a real shame that thy gave the gave the Tony that year to Sara Ramirez who had nowhere near as difficult or big or important a role in Spamalot. Clara is really the co-lead of Piazza, not a featured or supporting role. Sara and Kelli weren't in the same league in terms of role, performance or anything... Sara was of course great in her role, but come on. And if it wasn't going to go to Kelli that year, I also can't believe it didn't go to Celia for Spelling Bee over Sara in Spamalot.
I will say I think that somehow, despite Renee being very good (but not in the same league as Clark as an actor or musical theater singer) and so famous, the young lovers were the center of this production, is how it often felt.