I'm still using mine. I swore(just yesterday i believe) that I would not babysit my battery. Well I am. It is sitting in an ammo box on my living room floor charging away happily. I might switch the charging to work where I tend to remain in 1 room for a few hours at a time.
But If/when I do change I am going to go with individual cells and a holder. There's a guy on mtbr.com that makes holders that you build(screw and wire together) to your own specs. You can use 2, 4 6 or more batteries. Charging will be a little more difficult but at least you can determine which cell goes bad. I am also going to get a decent charger because that might be the problem w/ MS. This guy also makes powerful headlamp kits that you put together yourself. All the kits seem simple with a little soldering skill. I don't have the guys info with me but will post tomorrow if folks are interested.