First of all, I definately prefer old tech when it comes to battery chargers. You can not make a big enough transformer based battery charger to satisfy me. However, I finally took the dive and purchased one of the new switch mode battery chargers. I must say, I am suitably impressed!
I purchased this charger in a Black and Decker factory outlet store on the Oregon coast the first weekend in June. The store was having a sale where some items were discounted as much as 50%. The one I purchased was a factory refurbished unit and I gave about $35.00 for it with 40% store sale discount.
The charger is the fully automatic 3 stage 40 amp continuous charger with 110 amp engine start. It appears to be a fairly well built charger. I have only used it a few times to fully charger a couple of batteries, but it does its job very well. It has a number of features I will probably never use, such as alternator test mode.
One of the nicest features of the charger is its weight. It weighs a little under 10 lbs. A transformer based charger of this capacity would easily weigh 75lbs or more!
It also has a battery recondition mode. A battery if left in a fully discharged condition (someone left a light on in the trailer a number of weeks ago, etc) will undergo a chemical reaction called sulfation. You can usually tell a sulfated battery by the smell when you are trying to charge it. Anyway, this charger has a mode where it claims it can restore a sulfated battery to useable condion. I understand how this is done manually, but this charger has a mode where it can do it automatically. I haven't tried it yet (hopefully I never need it). But its nice to know it has that capability.
Anyway, I think this is a good battery charger for the price, with lots of features. It also has a 5 year warranty. Haven't seen a warranty for anything electric/electronic with this long of warranty in a very long time.
Here's a picture of the charger. sorry for the poor quality.
Mitch