Its a good deal considering the retail on this system is $150 and they don't go on sale often but the price has been lower in the past. Holiday 2010 Target had White DSi's for $113. IMO especially with the 3DS out now you were better off buying it back then if you wanted it back then and you would have gotten to enjoy the system already for quite a few months.
The white DSi gets dirty very quickly since it holds dirt easily due to the surface texture.
However the black DSi (I have one) gets little white marks as scratches on it, sometimes these can be rubbed off but not always. Even though I keep mine in a case all the time and only take it out when playing I still seem to find little white scratches on it.
So both have pros and cons.