One of the difficulties with the iPB-10 is that you can't just go to a guitar store and try it out. Most of the negative comments I've read online are from people who've never used one and just don't have a clue! Here are some of the frequent complaints and my take on them...
The iPB-10 for $499 and an iPad for $### is too expensive!
If you don't own an iPad and aren't looking for an excuse to buy one, this pedal is not for you. Save your money and buy something else. But consider the advantages of an iPad before you walk away from this. For most people, your next computer/laptop ought to be an iPad. Once you have an iPad, $499 is a reasonable price to pay for the best multi-effects pedal in the world!
I am going to break my iPad (alternatives: spill a beer, drop a hammer on it, break the screen with a misplaced stomp, etc.)!
Most of these complaints are a little silly. Spilling a beer on ANY equipment is a bad idea. That doesn't make the iPB-10 bad. Granted, it's more cost on the floor than some setups, but if you are throwing hammers around and stomping on your gear like a fool, this pedal isn't for you either. A lot of us are pretty careful with our gear, and I don't think this is going to be a problem. Apple designed the iPad to take a lot of abuse. I am an IT guy and I work with a lot of iPad users and have yet to hear of a busted iPad screen. They are much tougher than laptop screens. 
If you can't stand the thought of stomping near it, you can use a dock extension cable (not USB cable) so that the iPad does not need to be on the floor. I generally use the extension cable for practices for easy access to tweak settings, and then dock it for gigs. I do not miss getting on the floor to tweak settings. If you get an Apple Smart Cover for the iPad 2 or 3, it is magnetic and holds the iPad securely to a metal music stand. It is seriously sweet!
What is a valid complaint is that this gear is not meant for all environments. If I were gigging in a bar, I wouldn't bring the iPad unless I carried it with me on every break, before the show, after the gig, etc. Not a lot of people may be interested in stealing a guitar pedal, but I'm betting a lot of people would love to get their hands on an iPad. Make sure you register your iPad with Apple's "Find My iPad" app! In a rougher setting, I wouldn't even consider the iPB-10. Also be careful about using your iPad outside on a hot day. Once it overheats, it will shut down and no more screen for the gig.
For the price of an iPad and iPB-10, I could get xxxxx instead!
If you are after a certain sound or tone to make your guitar great, don't look at multi-effects pedals. Build a pedalboard. Multi-effects are for those of us who are trying to get many different sounds out of one rig and need to cover a lot of sounds with just a few stomps. This is where the iPB-10 shines. I can't think of another pedal that handles patch management better. If you do a lot of cover tunes and want the perfect patch for each song, GET THIS PEDAL! You find the patch you are looking for quickly, edit new patches quickly, and be able to build your set list from the couch, car, train, or plane. The cost of old iPads is coming down, so the initial investment is getting lower all the time. I don't recommend the original iPad. It is very slow in apps like GarageBand. If you can afford at least an iPad 2, that would be preferred.