SuiteCRM

It's easy to use and to customize. We've adapted to some of our internal processes and at the same time we adapted some processes to the SuiteCRM way.
Has a a lot of features and some new one are released frequently enough.
As an Open Source project is easy to integrate with other platform.
Ii love the "no license" approach because I can't think of a CRM solution not to be used by all the peopple in a company.

Community support is not always very quick, but is part of the game.
Some integrations (Google calendar) are still not completely working well.

The principal advantage is that you can log everything of your sales process: contact name, opportunity, customer, etc. But this is normal for a CRM. Everything is on a db mysql or mariadb that you can dump without problems.

There are several problems. Many module are buggy, for example the mail module, when you send an e-mail to a customer, he receives the mail apparently from himself; even if it is a two year old problem, it is not solved. So there are many issues opened on github, even extremely important (if you cannot send an e-mail with a CRM is a big problem...) not solved for months or years. The simple imap retrieval from a dovecot server doesn't work. The support is based on volunteers, but many questions don't find an answer. The installation is a bit a mess, because compatibility matrix is not respected everytime, so you have to find the proper mysql/mariadb and php version that works for your operating system (ubuntu in my case). The interface is very old style, which means you waste lot of time for doing things with an UI that doesn't help.

SuiteCRM allows us to add custom fields and change practically every screen and view, as well as data exports. This is critical as we refine our processes and change direction, we are able to reflect those changes in the CRM that we are using. Because of its Open Source foundation, we can change things pretty deeply, if we choose to.

There are sometimes slowdowns that make for a bit of "click and wait" syndrome. These have usually resolved themselves; in some cases we've had to have our sysadmin dig in and adjust some things to speed it back up.