Personally I quite liked the series... a big cast of characters, every character is quite differenciated from the rest and has his own personalities... heck there is at least an episode dedicated to each character, and I quite like that
And while the action part is not an integral part of the series, it is quite well done... heck some of the best fights I've seen in anime are from this series
For those who wish to delve a little more into Subaru's Seichirou's relatinship, read the Tokyo Babylon manga/OVA as someone already mentioned.... its a prequel to X.