Reading this thread, it seems the biggest problem with dungeon tiles is that a lot of you guys are trying to use them to construct rooms that match the ones in published modules. This is, in my past experience, and hopeless endeavor. I simply use the battlemap.
I do, however, own three sets of dungeon tiles, and for me they are a godsend. The trick is to design your encounter areas around the tiles, drawing inspiration for the tiles. I run my own Forgotten Realms campaign, and it's going wonderfully, but the PCs are 6th level, so I'm very accustomed to designing encounters.
I start with a concept, select my monsters, grab an appropriate combination of tiles, and then lay them out. I play with them for a while, adding elements here and there, throwing tiles in and out of the mix. My crawls are usually delve-size (3-4 encounters) in order to facilitate story-intensive, 1-session excursions that can be done without an extended rest. I then put the tiles in a little Tupperware bin, set them aside, and when my players reach the dungeon, I begin to lay them out, easily remember where each goes due to the smaller size of my dungeons.
I have a few different sets that easily mix and match, so I don't feel limited by my selection. On the contrary, I feel like having the tiles adds to quick, creative design. For example, I wanted to design a underground cultist hideout for the more sinister members of The Order of the Blue Fire. Using only tiles from Halls of the Giant Kings, I assembled the dungeon using staircase that decended into a waiting hall, off of which was a store room (a 4x4 tile with a 2x1 supply case), the cultist sleeping chambers (a specific tile), and an empty room containing the giant table. Then they decended further, through a few more rooms, then then I realized I wasn't sure where I was taking this. I spotted the jail tile, and realized it made a perfect room for the Order to be performing arcane experiments are spellscared captives. I added a fireplace tile to the end of it so I could narrate the mood lighting (narrated as a dark, cage-filled torture chamber lit only by a burning blue fireplace), and put some plaguechanged gibberlings in a few of the cages.
It was an incredibly memorable delve that wouldn't have had such a nice centerpiece final-encounter were it not for Dungeon tiles. I think the key to getting the most out of your tiles is using them as tools for not only immersive gaming, but inspired design.