Personally, I've been VERY frustrated with basically all of the apps available and find myself using multiple apps for different things.
I love having my iPhone with me on brew day and it's much less clunky than lugging around a laptop, particularly if there's any risk of it getting splashed on — MacBook Pro's don't care much for splashing wort. So on the iPhone I've really enjoyed BrewPal for recipe creation — it is a nice interface, helps me get in the ballpark of various beer styles, and can export the recipes via e-mail. BUT it doesn't manage inventory and the brew timers are highly flawed. If you press the top button on the iPhone to put the display to sleep, the timer essentially stops.
I've also been using iBrewMaster, mostly to manage actual brew sessions and toyed around a bit with trying its new inventory management feature. I liked it for brew sessions and its reliable timers, but the app is really buggy and the inventory manager doesn't work reliably enough. BUT it's off to a good start. I can look at my recipes and at a glance see if I've got what I need to brew that batch (green = enough of that item in stock, orange = some of it in stock but have to order, red = not in stock). If they could just work out all the bugs, I may go back to using it.
In my quest for the perfect brewing app, I also tried Beer Alchemy's iPhone app and basically had to write off the $4.99 I spent for it. It's way too "click" heavy to do things. Though it does manage inventory nicely, you have to click through like two or three times from a recipe just to see if you've got enough in your inventory to brew that beer. Not cool. I want to see IN my recipe view whether or not I have what I need to make a batch of that recipe. It's Mac desktop counterpart isn't too bad and it is nice how the two apps sync together, but it honestly reminds me too much of working in a spreadsheet that's been converted into an app. It doesn't have a slick layout or interface, and there are facets of using it that make pen and paper more appealing. (Is that even possible when I'm a web developer/Mac geek?)
I tried BrewTarget, an open source app for the desktop ...and closed it after looking it over. Yeah, it looks, feels and operates like open source. Onto the next app.
I briefly tried BeerSmith2 and it reminded me too much of Microsoft Office. I hate Microsoft...and hate their Office products. So yeah, onto the next app. Oh wait, that's it?
I've been seriously contemplating writing my own web application to specifically handle inventory (well) and work closely with recipes and batches from those recipes, making it easy to see at a glance whether or not you have the stuff to brew a batch up, along with a few of the calculators to help measure out your assets that you need for brewing. But it's a lot of work and I'd need some help to ensure all the calculations work right and whatnot. I've got the UI design and development experience and think I could come up with something nice and sexy — but I'm a lazy home brewer and would rather just sit at home and drink my home brew, hoping someone else would just make their app work right AND look awesome.