For anyone interested, Best Buy currently has Split/Second on sale for $20 in store or online.  Not a bad price for this game, so I think I will go ahead and take the plunge.

As well you should. I finally S-Ranked it, and I'm still addicted. 8-player rooms tend to be full of people who enjoy the game and are less likely to refer to others using slurs of the ethnic/gender variety than other games.  Little weird online sometimes, no rooms, no people, but that's not too common, and the other 99% of the time when it is working great, it is FANTASTIC!
 
After hours and hours, I can still FEEL the adrenaline dump when I start driving in this game!!

Saw this earlier and ordered, hopefully the in-store pickup goes without a hitch because I haven't even gotten my first confirmation email from them yet.

how are the achievements?

The achievements are very achievable!!  This game is my first S-Rank.  It took quite a while, but it was easier (I think) to go through Season Mode (offline) and take 1st in every race.  Then I focused on pulling the specific power-play achievements (they're all hidden, so I won't spoil them, but they require you to wreck a certain number of opponents with specific power plays).  With all that practice, I still had a hard time getting my online form up to 1, but it was a blast.  The 360 S/S community seems to consist of only two groups of people:  those who don't talk at all, and those who are not huge jerks.  Weird, huh? Last of all, I worked on the "Beat The Team" achievements. Most of the other achievements you'll pull off while working on these specific groups.
 
I'm sure you'll find your own way through, that's just what I did. Some specific achievements required tons of repetition, but I finally got it, and the game is still good enough to keep playing after all that!  That's saying something huge right there!!

no longer 20 dollar? i jus went to best buy site and its 39.99