I've tried the Optimate 6 with Deep Cycle, SLAs and regular lead acid batteries and had success with all types so far.
Marginal batteries were fixed with one pass of the Optimate 6, while batteries I thought were probably gone but worth a try took several attempts before they were recovered.
Optimate 6 has already saved me over $1500...

I recommend anyone who has a store of marginal expensive batteries to buy the Optimate 6. Even if you only save some of your batteries, you'll still be way ahead.

I've had an optimate 2 for ages trickle charging the track bike doing a superb job. Decided to finally add the optimate 6 to the shed as switching the optimate 2 between 3 bikes was a nuisance.

Left the street triple r on it over the week, never had it start so quick. Best bike charger ever

I have a collection of SLA batteries here in the workshop and have found this charger will actually test the condition of the battery as well as charge it correctly.
Even though the terminal voltage may be okay, the condition of the battery is tested so I can throw out the ones that don't come up to spec.
If you need to maintain lead acid batteries, this would be the charger of choice.

I've got 2 Optimate 4 chargers in my garage now, keeping my motorcycle batteries alive when I can't be riding them. When I saw that Moto-Tech were now selling Optimate 6's for cars, I had to have one!

My parents own a POS old Triumph car with typical British electrics, and were on a first name basis with the auto club guy. I bought them a jump-start pack, but they're not mechanically minded so that was a waste of money, so I decided that the Optimate 6 would be the "fix".

I was right, their car now starts first time even on cold mornings, and they haven't had to call the auto club since.

The electrical connectors have been changed to bigger, more robust connectors on the Optimate 6, and so the optional cigarette lighter adapter from my Optimate 4 purchase won't fit my Optimate 6 for use on my parents car. I'll pony up the $25.00 or one, as my mum has problems plugging in, and unplugging the heavy duty Optimate 6's connectors.

Picked up an Odyssey PC1700 battery from the local tip (shhh) Was only a year old according to the date stamp on it. Checked voltage when i got back, 2.4V! So i hooked up the OptiMate 6. After a few hours i was shown the red light telling me the battery was not taking charge. HOWEVER, as per the instructions, after an hour i reconnected the OptiMate 6 and tried again. In fact it was on the 6th attempt that the battery was then able to be re charged and reached the green light. Passing the 12 hour test with ease. This battery now jump starts classic V8's at local car shows most weekends. $500 worth of battery, saved by a $140 charger! do the math!