I bought this one for retro console repair. I've replaced save RAM batteries in SNES and Genesis cartridges, an NES expansion audio mod, TSOP flashing an original Xbox, and other things. It works great. I think I got it based on your recommendation in the "have you repaired anything lately" thread.
Just based on what I've used it for, it's paid for itself and the other tools I bought (solder sucker, desoldering braid, some resistors, the batteries, and some nice 60/40 solder) a couple of times over already. If I had to ship those cartridges off to get a battery replaced it's around $8 + shipping for each one from some sketchy guy on eBay.
I've also bought some three-prong CR2450 and six Japanese Mega CD backup carts on Amazon, replaced the batteries, and put them in replacement region-free shells and sold them on eBay myself. Made a tidy little profit, since original US ones go for $60 each. I sold them all for $45 + shipping in less than a day. After my costs and eBay fees I made around $150 for an hour of work.