Ask HN: Which libraries, components or API's slowed you down when building MVP?

I figured if there's anywhere I can get a sharp list it would be here.

I'm looking for input / feedback / braindumps of any tasks that you tried to complete using libraries, components or APIs that took you more time than expected to deal with when building your MVP, or any web based project, really.

Programming language is no barrier to this question, and I'm not looking for any lanugage/framework/library bashing. Just things you wish existed that didn't. It doesn't matter to me whether you wish a special GEM existed, or a library in another language was missing, or if you had a manual hack to make it all work.. I'd like to know all of the above.

I'd like to collect a list of them to see if there's something I might be able to tackle in a language I know, or a new one I can pick up.

The kinds of things popping in:

- sending / receiving email through a mail service - reliably creating PDFs - editing images easily - user/session/role management - payment - reporting - notifications - application monitoring

Thanks in advance,