Is there any way to "ask" Marketplace for any updates without just waiting for them to pop up? Coming from iOS where you could just push the update button and it would refresh, there doesn't seem to be any way to do that with WP 7.5
I don't know how about others, but I don't have any button to refresh app updates on my iPad. If you mean OS updates, than you could check that when you connect your phone to Zune.
I think he means app updates, and by going to the updates tab of the iOS app store it pulls any updates for your apps, so it functions like a show available updates button
Well starting marketplace works almost the same way, I sometimes get updates notification after starting it. But it's true that not all updates are shown right away. That is not a big deal for me, I miss more auto update feature where apps would be updated automatically without clicking "Update all" button