Yes, I'd love to co-locate. And I will very soon

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One main thing is you OWN the servers you co-locate, they are yours, you don't pay an extra fee per month for a larger hard drive etc. If you need to do big upgrades to the server, you can do yourself and don't have to pay a fee.
You can also setup hardware firewalls and routers at your co-location spot, so once again, that would be your own. So it can be much more secure then a normal dedicated server would be.
I plan to buy a dell server or two this year and co-locate them in a local datacentre here in Sydney, Australia. I'll keep you posted on my progress with that.
- Shane.