I've been with Sprint for a few years and it could be better. My biggest gripes with them are coverage holes/gaps and their voicemail.
Anytime I drive down 85, through Rowan County, I go from having the strongest signal possible to a completely dropped call instantly. Just seems to be a lot of gaps with Sprint but overall, it's getting better.
Their voicemail sucks and I've heard a numerous other people complain about it. I miss a ton of messages because I'm not notified of them until well after they were received. My phone will just alert me all of a sudden of a voicemail message and when I go to check it, I find out I had like 12 new messages. Some of them came in a couple weeks before I was even notified. You have to constantly call Sprint and let them reprogram your phone. And contrary to what they tell you, simply hitting the "*" before exiting your voicemail does NOT keep this problem from happening.
I'm thinking about switching to Verizon.