Ahh yes, i know that sort well.
This guy i played a few times uses Crimson Fist SM but he uses Black Templar rules, i have no problems with this, as i was using my Saim-Hann painted Crafties as Biel-Tan.
Anyway, we rolled the D6 and he got the first turn, he decided that he was quite safe behind his wall, and did nothing that turn. So i sent my falcon up and started blasting stuff, he destroyed in his next turn with the missile launcher in his tac squad (which somehow moved 4 inches into range and still fired.. hmm)
After another turn he flew his assault squad over some woods in (damn jumppacks) and into my Scorps, now usually i wouldnt have any problem with this, since i have faith in my scorps, except when the marines assault they were 14 inches away, not 12. I pointed this out to him and his reply was "Its done now, ive started the assault (no dice had yet been rolled) and cant go back" and he also extended the range of his bolters rather substantially, from 2 shots at 12, to 2 at shots at 14..
Also, like one that was previously mentioned, he got all depressed and pissed off when i finally got 2 Wraithlords up there and started winning, and started flicking dice into my models... all that sort of irritating stuff. Bah.. I did eventually win, although my Dire Avenger Exarch needed his arm glued back on after a die hit him... and he made out that there was no way he could have won because Eldar are unfair... blaerg...
The best opponent ive faced was a World Eaters cult player, he used his army in a very fluffy way, not even firing his berserkers bolt pistols. He took his losses well, and didnt make a big deal out of an easy victory (i admit, i played *very* badly that game, made idiotic mistakes) and the game ended in a duel between my DE Lord and his Termie Lord, it had no effect on the game, i had already lost, but it was cool that he let me take his Lord as a slave as a consulation prize.