I own a xim360 and bought a xim edge this week. I've had the xim360 since 2010.
Anyone that says a xim is an advantage hasnt used one.
Xim doesnt = mouse and keyboard.
I'm excellent with mouse and keybaord on pc in games like bf3, cod and dayz.
The xim isn't a magical aimbot, you won't buy one and become exceptional, any good pad player will gie you a run for your money. You have got to accept that xim isnt the same as mouse and keyboard, it is close, but it is not the same.
The videos you see on the xim website are the same vids you see on youtube of 100 kills and 3 deaths with a pad, i.e they don't happen often, but those are the showcased vids.
Simply put, if you put the time in to a control pad you will be just as good, reason being the console versions of these games are so assisted they fight the xim.
This has never been more true than the current fps releases, blops 2 and halo 4, these 2 games are worse than ever with xim, many xim users on the forums are doing better with pad this time around.
Spend a day watching cod showcases on youtube from pad users. You'll see exceptional play from dedicated players. The same exceptional play being shown off by xim users who aremjust as dedicated.
I'll say it again, xim doesn't = mouse and keyboard. I wish it did, but it simply is only a rough aproximation, pad users are capable of the same thing, especially in blops 2.
Lastly, ms has gone on record saying the xim/ other mouse and kb adapters aren't illigal.
Personally my advice is not to bother, learn to use a pad, in the current and presumable future game releases, you'll do better.