Having used wealthfront.com for a couple months now after years of DIY ETF-ing, I have to say that I really like it's visualization of saving over time (the deposits show up on the graph, and they show you an "overall return" figure that lets you look at appreciation separate from deposits). I find myself more motivated to save, because the graph reminds me of my good decisions in a way that's rewarding.
As a result, psychologically, it's a little more fun to save into that account, so I do it more. When I was buying ETFs myself through scottrade and TD ameritrade, I would have to wait to have enough money to sweep it into my brokerage acct, then worry about the $7 commission. In reality what would happen was that I'd let the cash snowball, and a few times a year I'd collect all my cash (dividends from) into one account, like squeezing the last bit of toothpaste out of the tube, and when all the transfers cleared, figure out how many shares to buy, and do the trades.
I'm sure there are other ways to get this level of automation and convenience, but I really think there's value to the very simple interface that a service like wealthfront is offering (even after the fees): investing a spare $1000 in the checking account is just a one-click, fire-and-forget thing now, so I've been making deposits (above the weekly automated deposit) much more frequently, whenever I see a pool of unspent money stack up.