Coming a bit late but I absolutely love kettlebells. I think they're much more versatile and useful than dumbbells. I don't belong to a gym so I have a set of bells at home and for a while worked with an RKC trainer. I really like the books by Lauren Brooks and Tracy Reifkind, ditto for DVDs. And although KBs aren't cheap, certainly for me they've been a relatively inexpensive way to get in better shape. Between walking, kettlebells, and diet changes, I lost 35 pounds in a year.

KBs are worth it if you are planning to work out at home and/or limited to freeweights. You can build muscle and strength using them actually depending on your level of fitness. Someone who can bench 300 lbs probably won't be useful for them.

I like to do KB swings, one arm snatches, and single leg deadlifts. (Our gym only carries 60 lb as the heaviest which isn't heavy enough for certain things). All these exercises are replaceable using DBs except for the KB swing. For me, KB swings are invaluable and put it towards the end of my workout as an accessory.

If you are planning to use only KBs as a stand-alone workout, I think it's worth it for general overall fitness. (but I heard they are costly, so stronger you get more KBs to buy)

I use them at gym but pretty much interchangeable with dumbells.

I'm trying to increase my overall fitness and wondering if a kettle bell purchase would be worth it? Does anyone use them and swear by them? TIA!