I've been and to me it looked more weird than beautiful. Like something from the set of Farscape. The quasi-organic forms are almost disturbing. I was surprised the clergy of the time agreed to it.
Impressive sure, but in the way of "Wow, there is a lot of work in this weird thing"
Gaudí was incredibly ahead of his time with the design of the cathedral. Even as a non-believer I highly recommend that people visit this building at least once in their lifetime. It's unbelievable in person and I actually got vertigo looking up into it. It's a truly awe inspiring building and it's shocking that it was designed in the 19th century.
Impressive sure, but in the way of "Wow, there is a lot of work in this weird thing"