Ever since I got Planescape Campaign Setting back in high school, tieflings have been one of my favorite races.
In 2nd Edition they were supposed to be the half-breeds of a human and some other fiendish critter, though they initially had a standard set of racial traits. The Planewalker's Handbook let you swap those out for multiple rolls on a Tiefling Abilities table (it also had a table with random physical traits), and if you were into the whole Skills & Powers thing there was an issue of Dragon that would let you spend character points to start with things like wings.
3rd Edition kept the flavor and standard tiefling traits of energy resistances and darkness 1/day. I did not like it very much, partially because it had a level adjustment, which meant that you could not play one unless you started at a certain level (in this case 2). It was a really poor way of dealing with races with more/better racial features than the norm, especially considering that they did not scale and gradually became worthless.
The other reason was that it lost a lot of the variety from 2nd Edition. I am not even sure if the devils, demons, and yugoloth could even all cast darkness. It made more sense to throw in a variety of spell-like abilities and resistances, to help you mechanically justify the lineage of your choice. I get that it would have given the race a lot of real estate, but there is no reason why this could not have appeared in Unearthed Arcana (which had a lot of variant races), or a Dragon article.
4th Edition changed the flavor, making tieflings the ancestors of a bunch of power hungry nobles that were cursed as part of making a literal deal with the devil. I actually liked this origin, and it explained why tieflings in the art all looked the same and had the same racial features. They even published some racial powers and feats that let you shake things up.
At any rate, I am not sure what origin story they will go for in D&D Next, but I do not see a reason why being the offspring of a fiendish creature or being cursed for making a deal need to be mutually exclusive, or need different racial features. The idea with this tiefling homebrew is that you get a basic set of generic features, and pick a heritage to give you some variety (at this point it is just ability bonuses and spells, though an ice devil lineage would change up the resistance).
Since we are doing another playtest on Weds, I am going to see if someone will give this a shot with my infernal pact. If you use either of them, lemme know what you think.