Uptime and other service performance levels Other payment networks have scheduled maintenance periods as well as unscheduled outages but Bitcoin's network, being decentralized, can have varying service levels depending on:


which versions of the software and which nodes are used
the nature of the transactions (e.g., microtransactions or those originating from an eWallet sans fee, etc.)
several other factors.


What are key performance measurements that can be made for the Bitcoin network, and how can they be measured? If measurements are being made already, where are they available?
You seem to conflate several issues in your question. If you are just talking about "uptime", which your question title implies, then speed of transaction propagation or confirmation is not relevant. As long as your node is can connect to other nodes and send/receive data, the network is "up". If you send transactions that require fees and they don't confirm for a long time, that's your problem, not the network's.

That said, the "gist" of your question, about network health, transaction processing speed, etc, is not unimportant. There is a bunch of useful data on this site, dedicated to monitoring the bitcoin network: http://bitcoinstatus.rowit.co.uk/ that would probably get you started in the right direction. :)