Sprint unleashed a slew of network announcements this morning at a press conference in Chicago, and for the most part, it's just the news you'd expect: more LTE, more Spark, and more HD voice.

The 28 markets aren't listed individually, but Seattle, Cleveland, and San Jose all saw expansions, and Sprint brought its LTE coverage count to 471 cities today. The company plans to cover 250 million people with its LTE network by mid-year, up from 225 million now. Sprint Spark also added some cities, including St. Louis, Winston-Salem (NC), and Greensboro (NC). The company announced in relation to the Spark expansion that deployment of 8T8R radio equipment would soon begin to take advantage of that big hunk of 2.5GHz spectrum Sprint acquired from ClearWire.

Nationwide availability of HD voice was Sprint's biggest announcement today, you know, if you care about that stuff, and the carrier currently supports 28 HD Voice-ready postpaid phones and an additional 33 prepaid ones. International Wi-Fi calling was announced, too, with support for more than 100 countries in the coming weeks.

Finally, Sprint tried a little bit of Uncarrier-ing with a new network satisfaction guarantee scheme, offering new subscribers (or current subscribers adding a new line) 30 days to try the network. If you're not happy, Sprint will refund the cost of your device and waive all service activation and activation charges within the first 30 days of your contract (presumably the ETF goes away too). This guarantee starts on June 27th.