1st: "unrated" players actually have ratings - just you don't see them until 4 games are played.

2nd: Ratings takes many things to figure a rating: Your rating, your oppenets ratings, how many games you played, and how many games your oppenent played.

3rd: Until 25 games are played (Well actually until 100+ games are played), ratings will fluxuate a lot. That is why it is a "provisional" rating until 25 games are played. I actually heard it can take up to 400 games before a rating is actually set pretty well.

4th: Even if you don't see ratings change, it may change. For example, before a game it may be 1500.1, then after the game it could be 1500.4 - but since you only see the "1500", it looks like it does not change... even though it does.

5th: How the formula works, it is even possible to lose points when you win! (When you don't have many games played, etc...) But I believe Fencer made it so you never lose points for a win, so at those times your rating will actually stay the same.

Anyway, in short - ratings will do very funny things until you get many games under your belt. At least 25 games, but probable more then 100 games is needed before your ratings will settle down.