I am not sure why this is highlighted in the changelog, but voicemail support in 1.1 is still incomplete.

In 1.1, the "1"-speedial only works if there is a voicemail contact stored on the sim-card's voicemailbox field. Not all sim-cards have such a field. If you have a voicemailbox contact with a special voicemailbox icon next to it in the contacts sim-card subview, then your sim-card has such a contact and it should have been automatically imported into contacts and the "1" speed-dialling should work.

If you dont have such a contact, or you remove the contact it wont work. Unfortunately you cannot in 1.1 manually add such a contact, it has to be imported from the sim-card. You can edit it however. If there is several numbers, then the "1"-shortcut should always use the first one listed.

Hope that clarifies it.