I am starting a newsletter about UX

First, good luck. Second, improve that page double quick! :-) It's an uphill battle getting people to trust you with their email address and so you need to do at least the minimum to look reputable. My approach - which converts like gangbusters - is to include a screenshot preview of the newsletter. If you look up my sites above, you'll see what I mean. I get a conversion rate of 70-80%. Yet while your newsletter may be awesome, I'm hesitant to sign up because it just doesn't smell right yet.