Gorgeous George

I've started training BJJ recently (i've done a month of training, 3-4 times a week).
I've trained aikido for three years.

One problem i've always had in aikido is gauging the effectiveness of my techniques: to what degree uke is being compliant, as opposed to trying to keep their balance.
I've also always struggled to know if i'm using muscle - particularly, i've always found it hard to relax my shoulders.

The sparring in BJJ has really helped me with both of these, as uke/my partner is never compliant, and I cannot use strength for long, as I quickly run out of energy; therefore, I am forced to relax, and rely on technique (for the most part...) - and the results are never in question.

And although its groundwork of a form not practiced in aikido, I have just used the aikido principles i've learned, by and large: relax, try to use your weight/put it on a person, don't look to force a technique - use the space/openings offered to you, etc.

Dose anybody else here practice BJJ, judo, or any martial art that has sparring/non-compliant training partners?
What are your thoughts on understanding, and increasing your ability at aikido, through such training?
I know that i've really come to understand the necessity to relax (and how to relax), and the effect on my aikido has been instant.