Eventually, I managed to find the right combination to get my printer to show up on the iPad, and once I did I have to agree it works quite nicely. It is a little funky, though, in terms of just being a printer. The app has buttons to connect directly to pictures stored on the iPad, and it can connect with online storage from Box.net, Google Docs, Evernote, and Dropbox.
It can't print from the Safari browser, but the app has its own browser where you can enter whatever Web page you want and print it from there. It doesn't work with iWorks apps like Pages and Numbers, so printing docs from those apps requires some creative workarounds--like first getting them into Box.net or Dropbox.
As far as I can tell, I can use the Epson iPrint app with the Epson Artisan 710 printer without the need for a PC. The printer is connected to a PC--my wife's PC, and I couldn't mess with that set up or I could be at risk of great bodily harm or long cold stares. But, it seems to me that I could shut the computer down, or disconnect the printer from the PC, and that the iPad would still be able to communicate with the printer through the wireless network. Anyone who knows for sure can feel free to confirm, or correct me if I'm wrong.
For the record, Lexmark offers a similar app for its printers. The LexPrint app is also free, but rated only two stars based on customer feedback.
The Holy Grail of iPad printing is the AirPrint feature. Unfortunately, using AirPrint requires having an AirPrint compatible printer. As it stands right now, the only vendor offering AirPrint compatibility is HP. There are quite a few printers offering it, but they are newer models so if your HP printer is more than a year old it probably won't work. I have an HP LaserJet 1018 that is only a few years old and it didn't make the cut.
The good news is that the AirPrint compatible printers start at only $99, so adding one into your iPad setup probably won't break the bank. But, if you take a $499 16GB Wi-Fi only iPad, and then you add a $100 Bluetooth keyboard, and a $100 AirPrint compatible printer, the bill starts to become harder to swallow.
According to Apple, "AirPrint works with Safari, Mail, Photos, iWork, PDFs in iBooks, and third-party apps with built-in printing. If you want to print a photo and your printer has a photo paper tray, AirPrint will automatically select photo paper. You can also line up multiple print jobs and manage the queue right in AirPrint."
If it works as smoothly as AirPlay, I am sure it is a beautiful thing. And, if I were in the market for a printer, I would seriously consider the HP Envy 100.
The ultimate answer to the question of whether or not you can print from the iPad is "yes". You can, but depending on the printer you are trying to use, you may need to have a PC to get there, and if your printer isn't an AirPrint printer there may be some frustration and additional effort involved in trying to make it work.
If you have found some other app or solution that works, add a comment to let me know what you use.