My first reactions, in order of appearance - hope they will be helpful in crafting the UX:
1. After reading HN title: Why would anyone need a special site for Trial Period?
2. After first glance at the site: Aaah, it's only for 3 days. Why so short? Does the site help the companies make a good decision after these 3 days or is just a sourcing channel?
3. After noticing that the jobs aren't dev only: Great! So many job sites are focused on devs exclusively :)
4. After clicking "Start trial" link: Why do you want me to sign-in? I didn't notice this requirement earlier. Why Twitter? Why don't you provide some form instead?
5. After attempting to sign in with Twitter: Why do you need so many permissions? Update my profile? Post Tweets for me? Can I trust you?
6. After abandoning the sign-in and going back to home page: Aaaah there's "Pleas sign-in message at the top". It seems I was banner blind 2 minutes ago. So where is the FAQ, contact info, TOS and other stuff required to form at least basic level of trust?
So, as in case of many services it was a little emotional roller-coaster between hope, disillusionment and doubt coming form insufficient information. Fortunately all of these seem to be quite easy to fix :)
EDIT: A couple more of questions running through my head during the 1st experience with your site:
1. How will the trial look like? How much time should I reserve? (it would be great if such info would be part of Job Posting)
2. Does "Start trial" mean that I'll be instantly connected to someone? Should I expect an interview? Are the positins remote or on-site? etc.
3. Am I right to expect that the trial will be unpaid one?