i personally have 7 of hobby king's 4000 lipo hard case batteries and they are simple amazing for the money. I think between 4 of us at our club we have about 30 of these total. I have only had 1 personally fail on me and it was due to abuse and everyone else has had 0 problems. We've been running them for nearly 1 year.
I will reccomend them time and time again for those who are looking for a good inexpensive battery. Keep an eye on their website and try and order from the USA wareshouse while they have them in stock. It's about a 2.5 week wait if they ship from china.