I would never ever pay for a monthly subscription to a turn based strategy game like Massive Assault. I am a professional developer and I know how long it takes to get software stable and running and its just kind of a ripoff. Subscription based services only really work when there is a lot of content being continuously added or when running the game requires servers that do more than just coordinate games. I.e. an MMORPG requires lots of servers and often has continuous game content updates.
Take world of warcraft for instance. Do you think that Massive Assault is in the same class as World of Warcraft?
The one exception to this is www.lasersquadnemesis.com
which seems to do pretty well for a subscription based service. However, its supported by a single player game thats free, technically it has more content than Massive Assault, only costs three dollars a month if you go for a year subscription, and most importantly, its a much more polished game. Also, arguably, moves are resolved on their servers, so they do have to pay for those. Nevertheless, I personally wouldn't subscribe to this unless I was really into it because its still a lot for a simple turnbased game. (Laser squad's gameplay is more complex/less elegant than Massive Assault)
If a game doesn't require a multitude of powerful servers to constantly handle game operations and it doesn't have gigabytes of new content a year, then its a ripoff to run it by subscription. Period. Massive Assault is a simple, elegant and incredibly buggy game. I would pay a one time fee of fifty bucks for it if it was less buggy. As is, I bought it from an amazon.com seller for 15 dollars with shipping. And I'm dissapointed that after 2 years it still has issues.
You can't put out a buggy product, take people's money for it and then try to charge them a subscription fee to pay for bug fixes that should be free or fixed in the original version. A software company's business model should INCLUDE the cost of maintaining the software for the user base. If it doesn't, that company can't expect to sell future products to those same annoyed customers.