It's fun and well put together, but it gets old pretty quick...it's just way too repetitive and doesn't really suit this game's playstyle.
I can definitely see it as sort of a bonus add-on mode for kicks, when you get tired of playing normal matches(kind of like "Wager Matches" in CoD), but this isn't something that can hold this game up.
IMO, a day late and a dollar short....if this game plans on staying in the spotlight, it needs new maps(not just one...2-3) for normal 3v3/5v5, maybe even some variety...2v2/6v6/etc. I know I personally(after a year of playing) have grown very tired of the same ol' 5v5 Summoners Rift(3v3 isn't really my style). Sure the new champs every 2-3 weeks help, but even those aren't enough to keep me playing anymore...regardless of what new champs come out...we still face the same map and strategies over and over.
WE NEEDZ MO MAPZ RIOT!!!
Anyways...bottom line, it's alright, but it's not really what this game needs and all in all, it doesn't add a whole lot to the game.