remember, though, that ibu's are just one part of the picture. guinness extra stout can be up to 60 ibu and it seems less bitter and hoppy than sierra. gravity, finishing hops, alcohol content, carbonation etc. all have an effect on perceived bitterness or hoppiness.
i like sierra a lot but i do find its hop character a bit harsh compared to some other pale ales of similar bitterness. check out mirror pond pale ale from deschutes for the other end of the spectrum, and a favorite of mine is dale's pale ale from oskar blues.
you may also find that lots of hop bitterness just isn't your thing, which still leaves you plenty of options for beers to brew.