The testing space provided for us is of course, ostensibly, only for testing. The ability to instantly teleport from (almost) anywhere in the world to another space with no cost or cooldown however unbalances the game in interesting ways which can be 'exploited'. Most of these probably have been talked about before, but I'll just list them for convenience's sake. I don't think the real housing system that'll be released will feature these unbalances - for instance, there may be more limits placed on where one might jump back home, but we should have some fun for now :D
Unlimited Inventory
This one is pretty obvious - with a space just a /home away, you don't need to carry a lot of the stuff you might before. In fact, leave most of your non-essential inventory behind, because going back to retrieve them is now significantly easier than before, and leave more empty slots for fun stuff, like say cubimals.
Ancestral Land Abuse
You can stay in the A. Lands forever - as long as you /home out before the timer runs out, you can stay in the A. Lands forever by jumping between the A. Lands and your house 10 mins at a time. This makes the Completist badges much easier to obtain. Similarly, when facing Juju bandits, just pop back /home to avoid them, instead of running, jumping or ducking your way around the them.
"Free" Teleportation
Say you're mining in Callopee, and you want to pop over to Cebarkul to sell your rocks. Normally you'd use some energy to teleport, but now you call up your friend, and both of you move into home space, where you meet up. You follow him, he /leave, and voilĂ , you're now in Cebarkul, free.
Is it exploitable? Well, it depends on how much time it takes for both of you to hook up, and if there's anybody at the other end waiting to pick you up. One benefit is that there's no cooldown, and it doesn't count into the daily map TP / summon limits.
Like I said, most of these will probably be patched, so enjoy them while you can :P
Got any others? Share them below.