A lot of people seem to like this manga, but these are my honest opinions:
Very very bland. Nothing much happens, it's just about a group of friends trying to protect a little NPC with an uncanny resemblance to Aura. You have them going to different events and hanging around trying to solve the mystery (but if you watched SIGN or played the video games, this isn't much of a mystery). The big mystery of the NCP is a big disappointment as well (in my opinion of course). Again its just bland and unengaging. I had to force myself to finish the last volume.
It's cute, but not much else. Nothing really distinct about it. It has no personality at all. It's fine and it gets the job done, but it really isn't worthy of any praise in my opinion.
Most of the characters are fun to get to know. Each one has a distinct personality and everyone will probably find someone they enjoy. I found Zefie to be extremely annoying, Shugo was kind of dull, but the rest of the characters were enjoyable. Ouka, in particular, was a lot of fun when she wasn't hitting on Shugo. I found the obsession most of the female characters had with Shugo to be annoying as well. Even his sister had the hots for him (how original)!! I was very disappointed that .hack was turn into a harem-like manga, the franchise deserves better.
If you like the .hack franchise, you'll probably like this manga as well. But not always, I liked SIGN but I found this manga to be boring and dull. The story was not as griping as SIGN and the main characters (shugo, zefie, rena) were very shallow. Zefie in particular annoyed me to no end with her selfish attitude. I found this manga to be more of a harem romance then an adventure, which is disappointing given how wonderful the other .hack properties were. I can only recommend this to people who like very slow slice of life manga and/or harem romances.