Cryo glitch is definitely a b*tch.
The occasional scouting every 2-3 minutes is only going to catch it if you're lucky during that 30 second timeframe that it takes to pull it off. It also takes hit and run tactics completely out of the equation with no reactor to destroy. Oh, and good luck stopping it with 2-3 Anders on the opposing team.
However, that's not really the biggest turnoff of the game. There are various other glitches around that are equally as frustrating, such as the Arbiter dying as he passes over terrain or even simple bases in Rage mode(nothing pisses me off more than losing my 2-3 star arbiter due to something so stupid), or the freeze glitch with suicide grunts, and I even swore that one time I tried to fire off a MAC shot, nothing happened and I couldn't exit out of the MAC firing window(had to quit the match because nothing worked no matter what buttons I mashed on).
The biggest turnoff IMO is an almost complete lack of rigorous testing and balance changes. I mean, I think it's kind of ridiculous that nobody noticed that Grunts(well, none of the developers anyways, because I sure as hell saw it a mile away) don't counter air because of a tiny little mistake. It took 8 months to catch this little detail when it would've only taken 5 minutes for one(or two) of the devs to spam out 50 grunts against 25 Banshees and compare their performance against each other. It also takes about 2-3 months for each title update for a small tweak to the units.