Hi Crispian. Yes I have heard of GVO. But I personally use GetResponse. I think all email mnagement systems e.g Aweber, GetResponse, GVO, MailChimp etc allow you to do the same thing, to automate your business by sending a series of pre-loaded emails to create a relationship with your list, provide value to them and of cause promote some products to them so you can make some money. So I'd say choose the one that is appealing to you, learn how to use it and stick with it as long as you want to.
You can use this strategy to your advantage and increase your email list by giving people an incentive in return for their email. The giveaway could be free access to an e-book, a report, a gift hamper, or perhaps a lucky draw where people enter their emails and get a chance to win. A tantalizing offer is all you need for people to comply. For example: