If you've never played a Worms game before, WHAT THE CRAP, MAN?! STOP READING THIS AND BUY IT NOW!!
If you have played a Worms game before, this is one is still a blast. I played Worms Armegeddon when it came out, installed it on my high school's network harddrive so that every student who logged on could access it and play wonderfully silly local games. And, boy, did we. All the time. And you could hear cursing and laughter throughout the computer lab (followed by everyone alt-tabbing or turning off the computer monitor when a teacher came over to question what we were doing).
Almost fifteen years later, Reloaded has been brought back all that hilarious joy that's definitely on par with Armageddon. Local and online multiplayer is wonderful. Lots of cursing and laughter with friends (we don't have to hide it from any teachers this time). And really this is why you buy this game. Hilarious, goofy weapons to blow up your friends and curse/laugh when you fail miserably and accidentally blast yourself to smithereens.
What? You're still reading? All right, I can say more.
-Steam Achievements: a ton of achievements that make you work (some are ridiculously hard).
-Multiple platforms: I play on Mac and Windows both. It's nice to have an option.
IMPORTANT NOTE: You cannot play across platforms online (I have to play on my Windows laptop when playing with friends since most of them don't have a Mac).
-Map Editor is fun.
Some Blah things:
-The single player campaign is nice but it felt a bit short. For a really great extended Solo experience, you'll want to buy the DLC or the Game of the Year Edition. (GOTY includes all DLC and provides some excellent challenges.)
-A LOT of Steam Achievements are linked to the DLC, so you'll have to purchase them separately or the GOTY Edition to get all of them. BUT DLC only works for Windows. So even when buying GOTY Edition, you can only play the base game on Mac and Linux.
The game is worth the money at full price, but it goes on sale pretty often, so I recommend keeping an eye open to snag the game for $5 or better. (~$6.50 for GOTY)