We've used Klaviyo as our ESP for almost 3 years now and have had a great experience. It's so easy to put together campaigns and flows, to create finely-tuned segments and to see your statistics. Their support staff is also very helpful. I recently had an issue regarding deliverability and meeting Google/Yahoo's new sender guidelines. Shelly and Luan from support walked me through it, found the issue and helped me solve it!
