What Geryk said then holds up today, but more so. There are really a lot of options, and what makes the game that much better is the tight-knit community of friendly people willing to help.
This game is not all that difficult to learn, but it is very difficult to master. If you are looking for the Diablo of TBS, you will need to look elsewhere. You will have to think -- but NOT keep your mind on an endless sprawling empire with thousands of discrete individuals who all need to move, defend, or otherwise do their thing: the need for thinking comes from the way your cards (spells, if you like a fantasy genre) interact with the board. That is why many matches can be completed within 20 to 60 minutes; a game will be decided by turn 30, and a LOT can happen in 30 turns. There are uncountable billions and billions of combinations, and surprises lurking around every corner. You will never find a game this deep and complex that can be completed in such a short time.
The only drawback this game has, and for this reason I have given it a 9.0 instead of a perfect 10, is that the so-called AI used to test decks in single-player mode is truly bad. Additionally, while the game looks snappy and is full of lovely artwork, the audio is nothing to write home about, and, finally, the interface could have been improved in one or two places.
You can join and start up for $10 as of today (September 2008) -- if you like it, most people will give you enough cards for free to last you the rest of your life.