I had a Savage Model 11 converted to 358 Win. It's a sweet weapon. A lightweight, short action with the power of a magnum in a smaller, lighter kicking package.
The only real advantage of the 358 is that you can chamber short-action rifles for the round. If you already have a 308 (or are a fan of the 358 like myself) it's an excellent choice. For the beginner or somebody without a project gun, I'd recomment the 35 Whelen instead. It's a much more versatile round that you can often buy at your local gunstore if you need to.
One caution for those who want to convert the .308 to .358. Because of the greater diameter of the neck, certiain magazines (Remington 788 for instance) will not fit the rounds. The Winchester 70 is fine with it though. I converted a pair of magazines for my 788 conversion by driving an appropriate width wedge into the magazine which I had secured in a vice to prevent the sides from simply buldging. Worked well and didn't damage the magazine cosmetically.