I love Abaddon's versatility. He can be entirely viable as either a support or carry, depending on your build and ranking. I've been messing around a little with him so far and have found a core that I enjoy: Phase Boots, Blade Mail, Refresher Orb. Abaddon's damage definitely comes from his standard attacks, and each item compliments that by supplying ~80 damage altogether. Considering Refresher Orb and Blade Mail, this set gives Abaddon 19 seconds of time where the team will not want to target you (9 from using Blade Mail twice, 10 from using Borrowed Time twice)--that with his shield means you're avoiding a LOT of damage, and in most cases, returning most of what you take.
It's not an entirely gimmicky approach, though, since Blade Mail gives him much needed early-game intelligence and armor, and Refresher supplies the godsend regeneration. Phase Boots, of course, is to start the chase and get your passive off. In pub matches, I was able to dive the enemy base with just these items built and pull off an ultra kill, still walking away home-free. Abaddon is good fun.