Today I visited two iPhone developers to see how things went. First we visited Evernote, which makes a great note-taking app. This is the most useful app I’ve loaded on my iPhone so far (which has more than 30 apps loaded on it). Really killer thing? Take a picture of something with text in it. Say a sign, or a business card. Or a newspaper ad. Or a bill you received. Save it. Then, search for something on that bill. Wow. It turned all the text in the picture into something you could search for. This is the coolest thing.

The second app developer was Tapulous, producers of Tap Tap Revenge, the #1 free game (and was #9 on the overall list when I visited them tonight and they’ve been rising fast).

Some things I learned.

Evernote has seen 30,000 new people sign up for its service through the iPhone App Store (and many more have downloaded it but had existing accounts). Tap Tap Revenge, which was developed by Nate True, has seen about 200,000 downloads so far, which is made even more incredible because it wasn’t working for part of the day on Friday due to Apple not letting them onto the list at first.

Tapulous says they have several other apps (including a Twitter app, called Twinkle, that I got a first look at. That’s Mike Lee, Chief Architect, showing that off to me) that hasn’t been approved yet, and they are hoping Apple will approve their apps “any minute now.”

Here’s the videos:

Demo of Tap Tap Revenge. In this video you see Bart Decrem, CEO.

Meet Jeff Clavier, one of the investors in Tapulous.

Mike Lee, Chief Architect at Tapulous, shows off Twinkle for the first time, which is a new Twitter client coming soon for the iPhone.

Interview with Evernote’s CEO, Phil Libin, who shows me how his app works on the iPhone.

To give you some perspective on how much the world has sped up: in 1996 the hottest app was ICQ, an instant messaging client. The guys who started that company defined viral marketing. In the first six weeks that ICQ was out there they had 65,000 downloads. Tapulous saw that many downloads in less than a day.

I’d love to hear from other iPhone app developers, particularly ones that are getting praised, or are learning something unique.

Also, I’m hearing from other developers that getting apps approved by Apple is very difficult. Any tips for getting your apps through the system? Any news from developers so we can figure out how slow Apple is being in getting through the app backlog?