Absol is an awesome Pokemon, in both design and concept. I like that it's purpose to warn people of disaster, but it's appearance and classification as the Disaster Pokemon are misleading, making you think it's the cause of the disasters. The fact that it can learn Razor Wind doesn't help. I've used Absol in competitive 4th Gen, but I don't think I've ever used it in game. It was a fun, kind of gimmicky Pokemon because of Super Luck and it's high Critical Hit rate attacks, but of course it's poor Speed really holds it back.
Personally, I don't link it's Mega Evolution. They took a badass looking Pokemon, and made it super girly. It's head scythe becomes basically a decorative head piece to match it's super feminine hairstyle, and looks as though it can no longer serve any real purpose in a fight. The fur on it's chest becomes all really smooth and curls a bit, as opposed to to rough look it had before. It even looks like it should have been a Fairy-Type because of it's wings. I'd be more okay with it's design if that had that been the case. But when you get right down to it, they took everything that makes Absol the symbol of destruction, a scythe, a rough coat of fur, and an overall intimidating appearance, and stripped it away. Now, if would just smile, it would look like the symbol of super-happy fun time than disaster. When you get right down to it, Mega Absol looks like a My Little Pony/Pokemon Crossover fan art. I do not approve of it at all. They didn't even handle it's stat changes properly. Why would they increase it's Special Attack? By 40 points, even? By level up, it learns only two special attacks. Two! And they're terrible! Everything about regular Absol screams physical attacker, before you even look at it stats. If they were going to pump it's Special Attack, they should bumped it to a reasonable enough level that it's worth using, let along taking up the one spot you get on your team for a Mega Evolution. But 115 is outclassed by several regular Pokemon, including some Dark-Types and many other Mega Evolutions, who are also faster than it. I can't see any reason to say, hey, I have this Pokemon with base 150 Attack and 115 Special Attack. I should use it as a Special Attacker! 115 may be respectable, but it's not even worth considering when you have that much Attack. They should have dumped those 40 points into Speed to make Absol the physical sweeper it was meant to be, and should have already been when they first made it's stats. Seriously, only 75 before Mega Evolving? It just looks like something that should be fast, and it would have to be in order to warn people of disasters in time. And while 115 after Mega Evolving is good, it's not good enough. At the very minimum, 120 would be great, but I would have liked for it to have at least 130.
The bottom line is, aside from Absol's poor speed, it's awesome, and I dislike almost everything about Mega Absol.