Ho there Darkjester!
I'll second what Greyson said...about checking the local shop. The guy that I deal with will start cracking open boxes only when the next release is out...presuming he doesnt have scads of loose ones around from the release before that. Just gotta be in the right place at the right time.
But let me tell ya my experience OK? Cuz I hated the random minis idea too, but bought some because they were neat and I could use them. (I too come from a roleplaying background and didn't put much stock in playing skirmish games)
A: Turned out the D&D minis game is actually fun. I've still never gone really nuts about it, but as a diversion on an off night...its a pretty darn good one. (I also inadvertently turned my 11 yr old nephew into a gamer with them) Get a starter pack and spend the buck or 2 to laminate the map that comes with it. Makes a boss battlemat for the RPG too.
B: (this one has been said before) If you get a number of these things, you may find yourself changing the way you plan adventures. For example, I ended up with witha mittful of Azer Raider minis. I'd have never considered using Azer Raiders before, and I found myself writing an adventure that would give me an excuse to use them. Kinda broadens the horizons a bit.
Also, if you don't like the monster as written on the card, you can make up something to your tastes. (My azer raiders actually turned out to be small Lava Trolls) In this way, the randomness can be your friend, but you have to be willing to tweak your thinking.
C: Even if you only have one of something, you can use ye olde chess pawns and just say "these guys are the same as that one" (I use a bag of those smaller game markers that I got in the dollar store...the little pawn shaped one with the ball on top...got 6 each 6 different colors) Sure you may want a whole horde of zombies for an encounter, but how many times will you use a whole horde of zombies? Sure there's guys buying minis by the crate and ending up with a bajillion Goblin Sneaks, but my budget don't allow for that. I've been gaming for a year on a medium size cookie tin full of Harbringers and the odd other expansion pack.
D: I know theres a few places, Paizo being one, that sells small packs...like a goblin pack and an orc pack...but they still have asoortment in their packs (You may get an orc archer, orc spearfighter, orc warrior etc but they don't sell you 10 orc spearmen.) Keep an eye out though. I think its still just as cheap to buy a bunch of expansions and see what you get.
Ebay can kill ya if you don't keep a close eye on the fine print regarding shipping fees. I saw one guy charge a fair-to-middling flat rate for an auction with the notation that shipping can be combined with other auctions for another 25 cents. The fine print: it was 25 cents per mini, so even if you won a lot of 10, it was an extra 2.50. Sorry, the extra minis don't weigh that much or take up much space. There's good guys on Ebay for sure, but be careful.
E: Look to see if your shop has a dump bin of Mage Knight figs. Theyre going cheap from what I've seen. They're not exactly to scale with D&D (they're bigger), but you can always introduce them as half giant opponents, amazons, or something. Just pry off the bottom part of the clicky base and trim the rest to fit in a 1 inch square. (a Dremel sander is great for that if you have one)
In conclusion, lots of guys bemoan the random packaging because they feel "forced" to buy minis they don't want. I say go for it, and find clever new uses for what you DO get. Don't get too set in your ways. There's lots of gaming goodness yet to be learned.
Trev
EDIT_ a few guys have posted since I began writing this. The cartoon post illustrated why the game piece idea works better than substitutions.