I don't use grenades much either, but land mines can make a big difference in a battle. I like setting up a trap, going in and firing a shot or two, then having them chase me right through my little mine field. It can be a very effective way to deal with a tough enemy, and quite often a single mine is all it takes to kill your opponent, especially if you're using Bottlecap Mines. Raiders can be taken out with just a single Frag Mine if your Explosives skill is high enough.
I think my main concern with using mines is the potential collateral damage that could occur due to exploding vehicles. I am leey of accidentally setting off a chain reaction when there are neutral or friendly NPCs in the area and them getting caught in the middle of it(and then becoming hostile to me).
This is my first play-through(I am getting the GOTY version on Thursday and will try out the DLC then), and then after that I will be going to Fallout NV(depending on whether I should wait for a patch or not). Either that, or The Witcher or Bioshock 2(too many good games, too little time!).
When I try out Fallout 3 again, I will try to find a Mod or two and try a different type of character(of the evil, mine-laying type).