Question: I've been working at a newly established firm for over a month and I haven't signed a contract yet.

HR kept telling me that they needed time to prepare contracts for everyone, but I've asked almost everyone else in my department and they've all said that they signed their contracts 2-3 weeks ago.

I asked the HR girl again and she said "Wow, you haven't signed your contract yet? Ok let me check and see what happened".

I agreed to a starting salary until signing the contract, and was told that after signing the contract the salary would be set depending on my position.

The firm has come together in a somewhat experimental way, allowing people to fall into their positions naturally.

Now that I've been with the firm for over a month, is it to my advantage or theirs?

Can I leverage the fact that I'm now established and comfortable in my position (i.e. they would need a few weeks to train a replacement to my level) and can I use this to negotiate a higher salary?

Or is it to their advantage?

Answer: 
> 
> Can I leverage the fact that I'm now established and comfortable in my
>  position (i.e. they would need a few weeks to train a replacement to
>  my level) and can I use this to negotiate a higher salary?
> 
> 
> 

You can always try. It doesn't seem like much in the way of leverage to me.

You already agreed to a pre-contract starting salary and agreed that your salary would be set depending on your position. 

You will be going back on your word if you use your "leverage". You get to decide if that the way you want to come across in your new position in a new company.

It's not something I would do, but you could certainly try.
Given the model is allowing people to fall into their positions naturally your ability to leverage really depends on your performance over this first month. If you have demonstrated that you are performing at a leadership level then negotiating a leadership title and compensation should be natural. If you have performed at a junior level then trying to negotiate a leadership title will be very difficult.