In my opinion you should avoid this town if you want to explore a Bali that is authentic. But at the same time, Bali is an island that is changing rapidly and this sort of development is appearing all over the island. So Legian is perfectif you want to go shopping or have a good hotel or restaurant.
The beaches are also OK and you can surf there. Legian beach is probably the second most popular one in Indonesia, after it neighbour Kuta's. Double Six beach is also very popular.
There are some very nice beach clubs near the sea where you can drink cold bintangs, like the young Balinese!
I personally spent 5 months in Indonesia and my feelings about Legian are mixed: it's very nice to wander around, but at the same time the town is very busy and the number of scooters quickly becomes tiring. What I did like was going to the beach at night, during the week, because there was absolutely no one else there, and I could enjoy the beach while watching the fire works which I could see in the distance most evenings.