Well, as an impulse buyer, I saw some of the headlines and just pulled the trigger without looking at the bottom row of fine print of every single deal. You're probably thinking great, ideal customer. That happened about twice though before I decided to just not bother looking anymore until I have a real pressing need for some of the offers, due to some of the expiration dates. True, the notices are there, but they really are in fine print at the bottom of each deal's page. IMO, there could even be a simple warning at the bottom of the main page like "Some offers are only redeemable before a certain date. Some restrictions may apply - See deal page for details" Even something along those lines would be a bit more informative for the buyer and offer a clue that there are possibly certain restrictions to pay closer attention to. No more buyers remorse.
Sorry. That should only happen once per forever. Also, it is cause the link is to appsumo.com instead of to the deal (appsumo.com/lean) which skips the email page.
Initially pricing, and the 'only pay a little up front' aspect - no monthly contracts. I just charge up the account now and then. It used to be $1/1000 - dropped in Jan to half that (yay).
The setup wasn't too hard, and ntoper and a couple others were in IRC to ask questions of (and they provided some more support via email as well). I was a transition customer - started about a year ago when they were putting the polishing touches on their public offering. What I had was rather beta - no self-serve payments, reporting didn't work too well - but it's improved a lot in the last year (and even a year ago it worked for what I needed).
edit: the support was primarily me setting up domain keys and such on my end with DNS entries - the instructions weren't as clear to a non-sysadmin mortal such as myself a year ago.
So, pricing, pay as you go, IRC support and friendly people. Does that help?
Interesting. I've liked Sendgrid since when we've had issues of peoples email going to spam folder they are pretty helpful in tracking down why. (mostly saying gmail is a black whole (: )
I hadn't learned of sendgrid prior to going with critsend. That said, critsend has been fine with supporting my few issues, and until they let me down I'll keep trusting them :)
We do pretty high-volume newsletters and are using Silverpop now and Lyris/EmailLabs before that. Silverpop is OK (the frontend UI is kinda crappy, the API is functional but ugly, and the backend is PowerMTA which is pretty solid). They don't require double opt-in and give you control over the unsubscribe process if you want it. Once you start sending millions of messages a month, the pricing on MailChimp or Constant Contact (or SendGrid for that matter) doesn't really scale.
Silverpop was also recently hacked. I imagine email service providers make for easy targets. Email addresses are easy to sell, but aren't typically protected as well as obviously valuable information like credit card numbers.
