The sooner you get paying users, the better, because then you can figure out what they really want and move in that direction.
Depending on what kind of users you have in mind, HN may or may not be a good place to find them. There are plenty of products, like patio11's stuff, that probably don't convert at all from HN since we're not his target market. Maybe find a niche and concentrate on that?
I'd just use email or the phone for feedback.
1. In case you do not currently have a marketing site that lets people signup for an invitation to the beta, stop all development and create the marketing site right away. Having this done before you code lets you gauge whether your value proposition resonates with your target audience.
2. Start sending prospects to the site (post to forums where your customers hand out, run some ads via adwords or facebook etc) and let them sign up for the beta invitation. During the signup, get some additional information in order to segment them for step 4 below. Be very clear that your product will be in a beta stage, so that customers know there may be bugs/unfinished features. Promise to grandfather in the beta customers for a significant lifetime discount once the beta is over (and actually do so when the time comes).
3. Code and get your product ready for beta. This should be the minimum viable product and you can call it beta v1.0. Now segment your list so that you allow only x customers for v1.0, then later y additional customers when you go to beta v2.0 and so on. This will ensure that you do not get overwhelmed with too many customers giving you too much feedback. Depending on your product, segment the customers based on niche, so that you can focus all your energies creating a product solution fit for that specific set. Each beta cycle should be iterative - learn, build, measure.
4. Charge for the beta v1.0. This will go a long way in validating your idea and your product market fit. If you are not sure what to price your offering at, go with your gut instinct. You can always increase or decrease pricing later.
5. Take feedback over skype, phone or email. If you start with a small set of early customers, it should be possible for you to spend enough time with them. Scaling using UserVoice can be done later, since you are limiting the first set of customers.
I am in the same boat, I plan on just releasing mine out into the wild. I want as many users as soon as possible so I can get feedback and tune features.
You should allow in as many users as you can handle the support and feature requests for.
One user can take up to 90% of your time, other times ten users come in and happily use the software with no complaints.
Take their feedback with gmail. Don't get too fancy.
Proactively ask for advice and comments. Sometimes people don't complain until they leave.