There is a battery chemistry and vendor that nobody has mentioned yet and they are the LI-ion NiCoMn Batteries from BMSBattery.
BMS Battery is the largest re-seller of Ebike products in China and NiCoMn is a safe, easy to charge chemistry that is lighter and more compact than LiFePo, but it doesn't have the number of "life" cycles.
The "old timers" here have long memories and there has been issues in the past with both BMS Battery and their batteries. A few packs have died a "melty" death[I know of two that are documented here]and BMS Battery has been notoriously difficult to deal with. Their website is a wealth of mis-information and calling to get a "straight" answer is nigh-on impossible. And shipping times can vary wildly. These "issues" are by no means exclusive to BMS Battery, more like the norm for vendors in China[the exception is Cell_man, our Dr. Livingston in the wilds].
But the "winds of change" seem to be blowing and recent favorable reports are starting to come in, mostly from our brothers "across the pond".
The thing about BMS Battery is, their prices are remarkably reasonable, but their shipping costs are somewhat high. Those shipping costs are less to Europe and there is a much greater following there.
Respected ES members such as Miuan, D8veh and Haste[who have not responded here, but may chime in]have been using BMS Battery almost exclusively for quite some time now and they have nothing but good things to say. Customer service has improved to a point that one no longer has to worry about what they will receive[if anything at all], but when they will receive their goods. And even that issue has been well explained by D8veh.
As far as their Li-on batteries are concerned, here is a recent link to some initial experiences with BMS Battery Li-on offerings. viewtopic.php?f=14&t=33566&start=45
But these are initial experiences, not long term reviews. These packs do not have the proven track record of a Ping, so only time will tell how they hold up.
But at roughly half the price of the Ping[and many are on sale now], they are worth consideration I.M.O.
Putting many models of their batteries on sale is a positive sign. Nothing is worse for a new battery[of any chemistry]than "sitting on the self" and since BMS Battery stocks 100's, if not 1000's of batteries, putting them on sale would appear to represent an effort to "move" them so they don't get "stale".
There has also been reports of BMS Battery upgrading their cells as better ones become available.
If I was in the market for a non-Lipo pack[and I'm not sure the O.P. wants to go there yet], i would order a Li-on from BMS Battery.http://www.bmsbattery.com/50-battery-pack