As some of you who are familiar with my reviews and strange posts may know of my dislike of Chris Claremont (I'm not exactly discreet about it). And while he does write this series, I must admit that it does contain elements that make it somewhat important for most, if all, X-fans. Here's a few reasons as to why the title should be read:
X-treme X-men is a team led by Storm, so right away that means that Storm fans will probably want to check it out. No, make that almost definately.
Also featuring prominently are Bishop (in all his pre-M-day 'glory') and Sage. Sage fans will definately want to read this title- it's probably one of the only occasions in which I've seen her appear frequently and take a leading and active position in a team. She takes on a varitey of roles throughout the stories- usually as a mission planner, coordinator and form of communication (think Otacon, except more useful), but she also gets to do the whole 'cop' thing with Bishop from time to time, because apparently one cannot have Bishop appear in a series and not end up doing the 'cop' thing. Her past is explored, and you get to learn more about who she is and how she became a member of the X-men.
Rogue and Gambit are in the title regularly up until issue 19, and fans of the pairing will definately want to check out the ones that include them. Featured in the title are events such as Rogue pulling Gambit back from the brink of death (not entirely to his wishes), one of the lines featured in the little Rogue/Gambit collage in Messiah War ("We've had our moments, remy. They're not enough, they've made me greedy. I want a lifetime."), and all in all a decent source of colsolation for disappointed Rogue/Gambit fans still upset at Rogue being in a relationship with Magneto.
Of particular note is Lifeguard, who not only debuts and is featured prominently in a large amount of issues herein, but who is rarely seen anywhere else. I mention this specifically because she's recently re-surfaced as being part of the X-men's 'Street Team'; a role which suits her powers and personality perfectly. Personally I reccomend picking up this title largely to become familiar with her- she's a fan favourite, and there's a good chance she may become important in the future.
Fans of Cannonball will want to check out issues 24 and onwards, as he gets some fleshing out. As much as I hate to say it, Claremont manages to depict Cannonball quite skillfully- though that should be expected, seeing as how he created the character in the first place. Also featured briefly is Lila Cheney, the rock star- you know, the one that's not Dazzler and that nobody really seems to mention much.
Other characters that appear herein are Red Lotus, Psylocke (she dies pretty early on), Beast, Wolverine, Jean Grey, Emma Frost, Professor X, Shadowcat, Thunderbird, Slipstream, Nightcrawler, Rachel Grey, Elias Bogan, Sebastian Shaw, Lady Mastermind and others.
The series also ties into events that occur in the main X-men titles, which means that they kind of aid one in understanding said events a little better. Destiny's Diaries are a focus for some of the series, as well.
Now, for specifics:
Issue 19 features some lovely examples of Jean Grey being really pushy.
And above is from issue 23, in which she is really...corny. Issue 23 also features Storm and Sage essentially disavowing Professor X.
So that's all I can come up with for now.