First of all, this case is *big*. If you're looking for something to protect your DSi XL as you put it in your handbag, this is not it. Rucksacks ought to be able to deal with this wee beastie just fine, but if you're relying on a totebag or a reporter bag for your everyday needs, you may want to consider researching smaller cases.
The case itself is built like a tank, with a solid, non-flexible top and bottom. I reckon you could throw this down a flight of stairs with your DSi XL inside and there wouldn't be so much as a scratch (er, not personally recommended that you try this...). Inside the case is plenty of storage room. The bottom layer, for the DSi XL itself, is extremely snug and well-padded, and will hold your XL in place so that it doesn't slide around and scuff. The middle layer, which comes down to cover the XL, and is held in place with a small strip of Velcro, has room for your favourite eight cartridges. All of these fit fine in the little pouches, which cover them up to the "Nintendo DS" part of the label, protecting the label in doing so. The top half, or rather the inside of the lid, has holders for the large stylus and two smaller styli, and a netted compartment for accessories. I'm using mine to hold my HeartGold PokéWalker and two further games cartridges, and the case still closes with no problems.
So, if you're looking for something to protect your DSi XL from a possible nuclear holocaust, and aren't fussed about how much storage space the case is going to take up, get this. If you're looking for something to keep your XL in so that it doesn't get dirty, and size is an issue, look up one of the smaller, material cases. Personally, I would recommend this sucker, as it's brilliant.