I do not have any knowledge of Aastra phones, and will certainly look into them. However, I've a lot of experience with Polycom, Cisco SPA 5xx series, and Yealink T2x, T3x, T4x (we have a demo), and VP530 phones, and from these choices, my vote hands-down goes to Yealink. They've made a lot of smart choices moving forward with firmware updates and work great. They all (as of a month ago) support multicast, hotdesking, OpenVPN (which we use for a lot of locations), as well as all the usual choices - BLF, BLA, directory, custom logos, screensavers, etc. The T3x and T4x phones really have a more professional look and feel, and for the price, they're pretty great. The T38G (gigabit) phones even come with 10 side keys dedicated for anything (BLF, speed dial, hot desk, park, etc). The VP530 and T4x phones have many BLF, speed dial, BLA "buttons" but they're on screen "buttons".