Is there any reason to do all these pull-ups?

Solution 1:

Well, I actually did them all. There is no material reward or achievement that I could discern for finishing - James was pretty impressed with me, though, so there might be dialogue impacts somewhere down the line. I might note that I did this before throwing the party and he didn't mention it at any point.

(For the record, even though it uses paragon/renegade prompts to step you through the motions, your reputation scores do not change. Also it took probably at least 15 minutes...)

Solution 2:

Beating James' record has no effect at all, it's mainly for unlocking the conversations that occur while doing the pull ups (which are nothing all that ground breaking). Replaying it multiple times (why would you do that) only includes minor variations on the conversations that occur while doing the pull ups.

Completing the challenge will have no effect on any conversations outside of that meet up, and doesn't provide any kind of achievement (other than knowing you beat James).

While you are using the Paragon and Renegade triggers to do the pull ups, you're not actually changing your Paragon/Renegade levels at all by performing the pull ups.

I had read somewhere that inviting each member of your team up before the party would result in the contents of the party changing but that also didn't appear to be the case (I invited everybody up and nothing changed in comparison to my previous parties).