I bought the starter pack and several boosters 2-3 years ago. I used the miniatures mainly for my DnD weekends and of course gave the skirmish a try.
I never played on a regular basis but recently I tried it out with my gf and it was great! (except that she hates to lose )
Maybe I was just lucky but 1 starter and 5 booster packs were enough to play reasonable games with a good choice of creatures. We just split the war bands in good vs. evil (although it hurts an old DM like me to see devils fighting alongside demons LE/CE) so its about 60/40% of creatures in favor of the evil aligned side.
What especially lured me into buying the game in the first place was something other reviewers here seem to critizise alot: the prepainted miniatures!
I played Warhammer in my youth and usually just only gave the armies a black base coat - I just wanted to play not paint till my neck hurts!
Additionally the material is super durable and resistant, so they're easy to store and you needn't put on your silk gloves while playing

Conclusio:
A decent knowledge of DnD is not a must but it makes things easier of course (synergy in your warband, knowledge of the special abilities) The games are short and fast paced, there are a bunch of nice house rules you should take a look at if you like to change/enhance your gameplay and with some other board tiles you can easily make up your own missions (w new objectives)

Recently WotC released a 2.0 version of miniatures following the new D&D 4th ed. If these rule overhaul is any good I can’t say by now but I already ordered the new Dungeons of Dread starter pack including the new rulebook (I know it’s available online but I also wanted the minis) I dare say that the 4th edition might drive some more players to buy the miniatures because the rpg battles more than ever cry for a battle site on the table (arranging battles on a board with miniatures was never a negative point for me, it made things easier and more interesting) but the target audience may also change a little bit to „younger“ players. Thats usually only a problem if the rules are simplified too much and turning the game into pure dice-rolling. My hopes are, though that the simplification just tightens the gameplay not the player base ^^

Result:
replayability: excellent
duration: short and action packed
cost factor: depends on your geeklevel ^^ but i'd say reasonable
storage factor: very good, folded gamemaps (the quality is not that great) and very durable miniatures

I really enjoyed the shortwhiled and interesting games i had, whenever putting this game on the table.