Here are my use cases that cause pain.
1. Separate full node and wallet:
I run a full node. But that isn't the node with my wallet. Even though my wallet is encrypted, its safer to have it be offline when not being used.
When I boot up my wallet, it needs to synchronize -- you can pay before sync but doing so seems to take several minutes to get the txn sent to the network. Sync is slow given that I have another node all caught up. And my local wallet somehow NEVER seems to connect to my local node. And there seems to be an issue with 2 local nodes. Sometimes they confuse my router and so nobody can get > 8 connections until I reboot my router. This is very weird because I have manually set up port forwarding. So its like uPNP overrides my manual settings.
I am aware that there are other solutions, like stopping my full node, copying wallet.dat in, starting it, doing the xfer, stopping full node, deleting wallet.dat. restarting. But these solutions are painful...
2. Separate wallet and browser.
I typically don't browse on the same machine as my wallet, both for security and convenience (browsing via phone or pad). Its hard to get the payment address over to my wallet machine. Esp if I want to encourage anonymity by not emailing it to myself.
3. Payment URL
If I am browsing on my wallet machine, the payment URL doesn't seem to work for me. Granted I only tried it once and now cut & paste... it definitely not work on my phone (although that is a different wallet).