40,000 is five ranks in normal play, or if you're signing up for the first time, because the first few ranks are slightly quicker, will get you almost all the way to rank 9 (and then the intro tasks for Powerplay itself will add a few more on to that, which you'll need to complete to activate your rank benefits). Equally, there are 100 ranks to gain so skipping 5-10 of them is nice to have but hardly defining.i've never done any powerplay. is 40.000 a good amount? is it worth signing up for this dude before the cg ends?
If you were thinking of joining Mahon anyway, it's better to have it than not, certainly.
The question is probably more whether Mahon is the right power for you
- do you spend more of your time in or near Alliance space than in other parts of the bubble?
- do you like trading? (what about mining or exploring?)
If so, Mahon is probably a good choice of Power and getting this as a sign-up bonus is certainly worthwhile.
If not, you might find that you rank up considerably quicker in a different power (and enjoy it more), so that you can gain 100 ranks in that power quite a bit faster than you'd gain 90 ranks for Mahon.