During that period I saw everything from rogues rolling on +healing maces to warlocks needing on tanking cloaks, and I learned that you never can tell what you're going to get from a PuG. Yes, you'll get hunters who can't trap, mages who never resheep, rogues who mistakenly believe they leveled a warrior, and priests who Power Word: Shield you straight off the pull -- but you'll also find people who know their class well, or are in the process of learning just like you are, and who are fun to be around. I have now killed Illidan with a contingent of people who showed up to my PuG's back when I was a wee lolbaretank in quest greens and Heavy Clefthoof, so as a matter of personal experience I think PuG's are a somewhat underrated way to meet people who will later turn out to play crucial roles in how you experience the game.
I don't PuG as frequently anymore due to time constraints and increased time spent leveling alts, but I still hang out in LFG from time to time for the pure enjoyment of meeting new people. Yes, it is often difficult to PuG tanks and healers (I would submit, as someone who typically tanks or heals in dungeons, that it is also difficult to PuG skilled DPS), but a lot of people could make it easier on themselves than they do. If you're having problems finding a tank or healer for your PuG's, try these.