Let's see:
Game: Flames of War
At least one link it can be cheaply bought from:
http://www.thewarstore.com/battlefrontflamesofwarwwii.html
Cost of entry (minimum to play) and likely future costs: Depends. A tank company will cost less than a infantry company, while Mechanized lists cost the most. Germans are most often the least expensive, since their forces are more expensive points wise. Soviets will often be the the most expensive, since they require a lot of bodies. The good thing is that every you collect for a period will most likely be compatible. Tanks you buy will be useable in a same-period infantry list.
minimum players: 2
recommended players: 2-4
Recommended ages: I've seen children play against men who are around 40.
likely time to run a game: Depends. Most scenarios don't have a game turn length, so setting a time limit is an often used practice. 2.5 or 3 hour games are the norm.
What's to like: Good rules, constant releases, a time period for everyone, and the fact that you can use alternate models.
What you might not like: If your a modeller, painting things at 15mm may not be for you. On the other hand, each base is more or less a mini diorama. There's also the time periods. Early War can't fight against Mid War or Late War, Mid War can't fight against... well, you get it. If you start collecting Late War while everyone else is on an Early War kick (personal experience) you're going to be lonely.
Bottom line: If you're any sort of WWII fan, get it. The rules make sense, there's a plethora of armies and periods to chose from, and you don't have to actually use Battlefront models if you don't mind less-good looking models for cheaper.