The vast majority of people who have ever been stationed at Whidbey absolutely love it.
The very few who didn't are a vocal minority. Even more vocal are people who have decided they don't like it without having every been there, or having visited for a weekend or a week and had unluckily bad weather.
As with anywhere in the Pacific Northwest, the weather can be rotten in the winter/fall/spring but amazing in the summer/fall/spring.
Even in the winter it won't freeze much on the island, but will on the mainland a little more. Typically we are talking 2 days of snow all year and maybe 2 weeks total of freezing or below weather, ususually less.
Snowboarding, skiing (water and snow), hiking, camping, etc. are all phenomenal in the area and the scenery is just about the best you could possibly imagine with mountain backdrops and the insane greenery.
The people in general are significantly more friendly than most areas. There is plenty of nightlife activities if that's what you're looking for. The single things that are close are mostly in Anacortes or Oak Harbor (much more military feeling), or further away in Seattle. As far as Seattle being full of "hippies and rain" well you're sort of right but not really. It rains enough and it frustrates some people but that's why the place is so gorgeous. As far as hippies go, it's better than most places, and if you hate hippies you are unlikely to go to the parts of Seattle that they are in.
I aboslutely loved being stationed there and hope I can get back again.
If you are an outdoor enthusiast, have children, or want to be in an area where people are generally pretty awesome to each other, you basically can't pick a better duty station.
