I have disagreed and will continue to very vocally disagree with the assertion that Blade and Chain pacts are inferior. They really, really work out great in actual play when you realize that a bladelock is simply NOT meant to be a primary melee specialist like a fighter or barbarian. He's a caster who can also melee if he must, and should be utilizing his spells and invocations in and out of combat to gain every advantage, and those are some very unique advantages. My favorite combination is the tiefling fiend patron bladelock who takes hellish rebuke and armor of agathys as two of his warlock spells and combines it with fiendish resilience and Medium Armor Proficiency to be a crazy-good retribution tank. It's a super-fun build that just sucks up damage and hands it back all day long, and keps his THP topped off via fiend pact every time he demolishes an enemy. With the creation of SCAG's Booming Blade and Greenflame Blade, the bladelock becomes a lockdown machine, and is super fun to play.
The other one I love is the Great Old One/Chain Pact super-scout/spy character. This one is less of a combatant and more of an out of combat utility guy - at-will telepathy, an invisible mobile viewer who you can see through, the Mask of Many Faces and One with Shadows invocations, and spells like Friends and charm make for the ultimate social monster and scouting machine. And you can STILL do both of the above builds while having Eldritch Blast if you need to fight at range.
Warlock is just, IMHO, the best 5E class. It can do everything, and it doesn't have as much random crap to track, nor does it need to go all day without any way to do its thing if there aren't long rests available. Warlock is the energizer bunny of classes, and it combines well with every other class. For me, when I make a 5E character it comes down to 'Warlock or not a warlock' for class choice. The only other classes that compete consistently for me are Paladin and Rogue.