Hell. ♥♥♥♥ing. Yes. The Arena is a cruel, cruel Mistress - she will build you up, only to break you, & just when you think you're rid of her, she'll drag you back into her clutches.
In short, for those of you who are woefully unaware, Quake 3 is hands down the pinnacle of the "Old School" '90s FPSs designed by the original id Software team, using an entirely different Gameplay model than the Modern FPSs of CoD & BF. A more common term for it is "Twitch Gaming" due to the extreme level of reaction time required to truly match up against not only other Players, but also the Bots. To quote Dark Souls - "Prepare to Die", because you will, over, & over, & over.
Seriously, buy it. Once you do, get ioQuake 3 (Google it), & the Quake 3 Widescreen Fixer Mod.
Far as the Online Multiplayer portion (which is arguably 95% of the Game) fear not, for the MP Community is still extremely active, & if you're of the Competitive Nature, the CPMA Mod (Challenge Pro Mode Arena - the Standard in Q3 Competitive Play since nearly the very beginning) ups the ante by making an already difficult Game even harder (works both Online (PvP) & Offline (Bots).
See you in the Arena, challenger.... If you dare ;)
P.S. You're also going to want to check out "Defrag" at some point or another, if for nothing else then to just learn more about THE most insane Mod of all time, hands down.