Personally I find the Eldrazi matchup to be pretty heavily favoured for Grixis. (My spreadsheet says I have won 78% of my matches over the last 3 months vs Eldrazi with Grixis in mtgo leagues). All of Grixis' threats line up well against what Eldrazi is trying to accomplish, meaning you can ignore everything aside from reality smasher with young pyromancer, true-name nemesis and gurmag angler. Whilst you are defending on the ground with these, you should be chipping in with drs/delver.
The early disruption of daze/force/bolt/wasteland to stymie their mana, along with a quick clock means it's often easy to prevent them from sticking threats until you are well ahead in the damage race.
I tend to be more positive than most when discussing this matchup, so it may have something to do with my sideboard - I bring in 2 decay, 1 grudge, 2 needle, 2 strix and cut all the probes and therapies and the spell pierce. Most lists aren't running decays at the moment, but I find it helps with chalice/jitte/ratchet bomb/baby eldrazis (though obviously, it's especially important for chalice).

