Just so we're straight about this right off the start, the 5.10 Impact is the only shoe in the world with a learning curve to it. This is not your standard shoe. 

Five Ten have a history in climbing. They make little shoes with a special sticky sole that help people climb stuff, from rocks to buildings (they don't condone the buildings part though.) A couple years ago, IntenseCycles brought out a pair of shoes with the Five Ten sole on the bottom, and the rest is history. Now, they make a fairly diverse range (15 different MTB models at current) of shoes for you to blast around in, from race oriented models to the most casual looking riding shoes ever. 

We have the Five Ten Impact lows, which are i suppose about as close to a race model as you get from Five Ten.  The Impact lows have a couple of features beyond the sticky rubber sole that makes them stand out. The padding is thick and comfortable, as well as protective. The tongue is a wrap around sort, rather then the standard flap down the middle. This lets the Impact wrap around your foot and remain much more secure, so you aren't sliding around inside them. The laces are tough, and don't rip after 20 minutes. The sole, despite being the sticky rubber compound, is still stiff and supportive when you're on the pedals. This helps with power transfer, although obviously not to the degree of a clip-in shoe. The Impacts are made of something Five Ten calls "Action Leather Upper Material", which sounds like marketing gibberish to me. That said, they are super easy to clean off, which is handy for those muddy rides.

Simply put, the Five Ten can be one of the best upgrades you will ever make if you are a flat pedal rider. With these shoes, you will stick like you're glued to the pedals. Your foot will not slide around. Ever. It might come off, but it will not slide.  In fact, the learning curve comes from re-teaching yourself how to ride in Five Tens compared to a standard skate shoe. You have to learn to pick up your foot and reposition it, rather then just trying to slide it over. Riders have actually fallen over when they stop, simply from not picking up thier foot and remaining planted to the pedals. 

The fact that they are so sticky is the reason they might not be for everybody. Some riders simply aren't comfortable with how grippy the sole is. This also means you should watch what pedals you are matching the shoes up to. For example, if you were to wear Five Ten shoes with a pair of Syncros Mental pedals, you might never be able to get off the bike again. Pedals with super sharp, long pins can also tear the sole apart, since the rubber compound is softer then most. Strangely, even with the soft compound sole the shoe lasts quite a while, and wears fairly slowly. The stiff-ish sole, which was so helpful when pedalling, can be a bit awkward for walking around in. Its not uncomfortable, just...stiff. Personally, I'd rather have that stiff sole for when I'm riding, rather then worry about walking a bit funny in the parking lot. Finally, while its very much a matter of personal taste, I find the Impacts look kind of cheap, in a Wal-mart running shoe sort of way. But, performance more then makes up for it. 

The Five Ten Impacts are a brilliant upgrade. Nothing else out there grips like a Five Ten sticky rubber sole, even the competitors making similar claims. If you are a flat pedal rider, go get some now, and bask in the glory of sticky rubber. Just remember though, LIFT your foot, don't slide, or you're going to be lying on your side at the trailhead with all your buddies laughing at you. 

*** Solid advice from Terry:: Think about buying a size smaller then usual. The Impacts tend to stretch a bit, and they might end up being too big for you after a couple of weeks.