I bought one when they were on sale for $69 and it's a great bulk charger, but only so so when it comes to balancing.
If one is running 12S and are ok with 300 Watts, all one has to do is add a single cheap server supply and you're in business for less than $100. No need to isolate one server ground as is the case when running two PS's
The Thunder is a pleasure to use. The fan is quiet with a jet-engine ramping-up tone. The PS is actually much more whinny, but there is a simple mod for the HP Prolient to regulate fan speed. I wrapped my PS in some foam and duct tape so the "hot" chasiss isn't exposed.
The Thunder1220 is also easy and fast to use.
After scrolling to the batt. chem, scroll to the HVC, 4.15, 4.16, 4.17, etc. Then scroll to the number of cells, hit the cell check and hit go.
This charger really makes the most of it's 300 Watts, ramping up quickly and running a minimum of power-down checks. It gives you a single beep @ 4.00V and a steady beep when it shuts down @ the HVC.
I like the form factor of the charger, it has a sturdy metal case with a very interesting olive drab, metal-flake paint job[two things one wouldn't normally expect to see together]. The display is bright[adjustable], large and easy to read.
The not-so-good, The cell level leads, adapter boards and ports are crap. The wires are stiff and short and the connections are finicky and stressful to use.
And the balancing is SLOW. NBD for me, as I usually use a pair of Battery Medics on a single 12S pack, often leaving the pack on the charger, running at a trickle[.03 A].
There is an individgal cell resistance reading feature that I haven't used much, but it seems moderately accurate.
Bottom line- it's not a Hyperion 1440i, but it's easier to use and I prefer this charger for day to day use. So if you are staying at 12S or less, this unit is certainly worth a look.
P.S. Thunder has recently released a souped-up model of the charger that does 16S, but it's rather pricey at the moment.