Yes, it's good enough for some competitive use. Is it the best? Not by a long shot. That said, let's see where it shines:
- Great defenses (110/120) which is a shame it has so many weakness (6 in all) but also some good resistances in Ground, Grass, and Fighting.
- Decent speed (90) and a passable 80 Special Attack, but it doesn't really pose a lot of offensive threat (although it has great offensive moves in Psychic, Bug Buzz, Shadow Ball, and the all new Expanding Force).
- However, where it really shines is in its support Movepool: With access to Reflect, Light Screen, Psychic Terrain, Sticky Web, Infestation, Safe Guard, Trick Room, Ally Switch, Recover, and Helping Hand, it has phenomenal potential to aid your sweepers into dominating the opposition.
I particularly find the utility it serves in Doubles to be excellent, setting up screens, Psychic Terrain, and exerting pressure with Expanding Force. It can also use After You to further help your sweepers to KO opposition.
That said, it's not as easy to use in Singles where it gets overshadowed by more offensive threats, and even its Terrain set-up is not as effective as a turn is lost in switching etc. However, it is great as a lead, setting up Screens and Sticky Web, so that's a role you can try to use it for.
For Singles a good move set could be: Sticky Web/ Reflect/ Light Screen/ Bug Buzz (with Light Clay), or Sticky Web/ Psychic Terrain/ U-turn.
For double there's just so many good moves you can slap on it, it really depends on the rest of your team and what kind of utility they need, because Orbeetle can nearly pull off any kind of support needed.
Edit: Made a mistake saying it could learn Spore, that's wrong and has been rectified. Also as Crystal.Mad.Edison pointed out it can be a potent Weakness Policy Sweeper, so that's another use for it, with 3 attacks and Sticky Web.
That said, sumwun's answer about it being outclassed is 100% correct. Orbeetle isn't the best Pokemon for the job, but it can certainly help you out tons when needed.