We are drifting away from maxalt's initial question here - he posed the scenario where you are climbing to the initial SID block altitude, and there was NO FURTHER altitude clearance by ATC. It is true - it is ambiguous!
Judging by all the different opinions here, we DO need a 'definitive' from an ATC poster, and perhaps this should be raised by ATC as a safety issue due to the confusion, and terminology needs to be refined?