Dungeon tiles are cool and definitely can help enhance the immersion. Dwarven Forge is pretty much the pinnacle of craftsmanship and quality with their resin pieces. That being said, they are extremely expensive. There are two other issues I personally have against that style. full 3D dungeons block player (and DM) view easily and can be a pain to move miniatures around in where often I've had to get out of my seat to see what's going on. It also can be hard positioning a mini that happens to have its weapons reaching beyond the normal 25mm boundary. I've taken a huge liking to 2.5D as it counters all of these problems. 2D dungeons are made with walls that come ~1/4" up from the floor. They give depth/character to the dungeon, everyone knows where everything is at a glance, body/weapon position virtually never is an issue, and best of all they are fast and cheap to make.
A sample dungeon setup by tiles from 3ders.org
I'll start out freely admitting I borrowed heavily on others' work, especially that from Crooked Staff. He has some really fantastic tutorials and amazing tiles and his work is what I center all of mine around. He is frequently updating and adding new content so I'd encourage you to check his stuff. The room accessories are especially cool. For my tiles, I used his processes (and .pdfs for textures) with some extra enhancements of my own. There are 3 very notable changes/additions I used on my own; a more modular tile design, lamination, and interlocking tiles. Take pieces of mine, pieces of his, and/or pieces from elsewhere, but just do what works best for your design scheme.
When all is said and done there is not a perfect solution. There are 3 running methods, each with their pros and cons that I'll briefly lay out below.
Dwarven Forge uses an absolute 2x2 tile configuration with walls taking up 1/2" of space.
Quick to set up as everything is 2x2 or 1x2
Combat can get confusing; Do minis straddle lines the entire time? Do you not count the 1/2" spaces and diminish the combat area?
Extremely expensive if bought instead of crafted or printed
Most of their pieces are 3D, making it difficult to place some minis next to walls while also blocking the view of the players and DM
Both combat scenarios have drawbacks
Crooked Staff/Budget DM
Crooked's method uses 2x2 with walls on the outside and builds larger pieces whereas I try to keep to a smaller, 2x2 configuration.
2.5D design allows for greater visibility
Looser modular design can account for more complex layouts
To keep an absolute grid interior walls need to be 5' thick (although many map generators have a 5' buffer anyway)
Specialized pieces may need to be created for complex layouts
Minis are easily placed
True Tiles is a halfway point between these two. Their tiles are 2x2 spaces but they are not 2x2". Their spaces are 1.25" and any walls fill that extra .25" space as to be true to classic D&D hand-drawn maps that don't take wall thickness into consideration for combat. A nice touch is that their doors nest on top of walls so setup is even quicker.
Quick and modular.
If you use a ruler to measure spell effects you would need to recalculate distances
Crafting will be more demanding with thin walls and measuring to the 1.25"
Setup: 5x5 (6.25 x 6.25")
Minis are easily placed, but calculating ranged attacks can't be easily done with a ruler