Blizzaks are a softer rubber so they don't last as long as standard all-season tires on hot, dry roads.  But performance-wise there's no problem.  I've run them all year round, but I don't put a lot of miles on my car so avoiding the cost and hassle of swapping tires twice a year more than paid for the decreased tire life.  This year I'm running Michelin IceX's which are claimed to last longer in the summer.  So far I'm happy with their performance though I'd rate the Blizzaks a tiny bit better.  They definitely cost more than all-seasons, but you'll have to check prices.  Costco carries them.