Literally everything. Their reporting is useless. Their dashboard doesn't sort emails by date of send, it just arbitrarily organizes emails. And, when you try to gain insight into how your emails performed, you can't compare emails. You have to manually export emails into an excel file and - get this - YOU HAVE TO SORT THROUGH THE COLUMNS YOURSELF. You can't select what columns you want to export. AND, when you export a selection of emails, for some unknown (*cough*stupid*cough*) reason they include the daily stats of each email for up to a week. Why? Maybe they think that data matters?
Beyond that, I can't compare campaigns against each other in any sort of helpful way. With Campaign Monitor, I can compare campaigns with a couple clicks. With Hubspot, I can compare with a few clicks. Even Bronto - a company so old and clunky even other dinosaurs don't want to deal with it - can provide me relevant reporting. SendGrid? Nope.
And don't get me started on customer support. I need to sacrifice a goat, give up my first born, and do a 30-day juice cleanse just to get an email from support. Only after I threatened to leave FOUR TIMES, did they grace me with a voicemail (no call - just a message) notifying me that they'd be able to get back to me about my urgent matter THE NEXT AFTERNOON.
To say I'm displeased with SendGrid would be an understatement. SendGrid is more disappointing than my career choice is to my grandparents. SendGrid is more annoying than I was when I used to incessantly blast Yellowcard from my beat up Chevy S-10. SendGrid is a bigger pain in my derriere than the actual recurring pain in my derriere resulting from a bad skiing accident I had in Big Bear.
In conclusion, SendGrid is an even bigger waste of time than the 27 seconds it took you to read this review.