Apple has rejected another app from the app store because it considers it too similar to one of Apple’s own apps, and thus would cause “user confusion.”

The app is a front-end for Gmail, called MailWrangler, and allows users to check many Gmail accounts at once (unlike MobileSafari or Mail). It offers a similar interface as Gmail’s iPhone-optimized web interface, which shows conversation threads in context, and allows for starring conversations. The app developer says it works much like MailPlane on the desktop.

Nevertheless, Apple rejected the app because of the similarity, in Apple’s view, and also due to other issues related to editing account information.

Keeping with the famous science teacher saying of “every number must have a unit,” Equivalence (iTunes link) is the one-stop converter for all things units. Did we say “one-stop?” Why yes we did, because Equivalence can convert between over 260 units in 31 categories.

Once of the nice features of Equivalence is the ability for the application to auto update the unit conversions over the air, instead of through the App Store. So, if the developer decides to add a unit, or if a unit were to change, updates could get pushed out to the application.

The beauty of this application is when you flip your iPhone into landscape mode. Just like the built-in iPhone calculator, this application adds much more functionality when horizontal, including a calculator that can add units together.

Dave Taylor wrote in to tell us about several interviews he’s done with iPhone developers, and many have had less frustrating experiences than Mike Ash and Fraser Speirs.

Of 11 people he surveyed for his blog, I would judge that five had a positive experience submitting their app to the App Store, four were neutral, and two had a negative experience. The SDK received similar reviews, with six developers regarding it favorably, four were neutral, and one developer regarding it unfavorably.

Two of the developers with positive experiences said they submitted their app before the App Store was launched, and it was approved for distribution in about a week. The two developers with negative experiences submitting their app said that the most frustrating parts were waiting and the lack of communication.

Macworld has published a chat with the devs of one of the much-loved Koi Pond. Of course, the weird thing about Koi Pond is that it’s more of a nice iPhone demo than anything else — but just the same, it’s cool to hear from designer Bill Trost and engineer Brandon Bogle.

They used to work on MMOs for Sony (and now work with a new company called Trion, also developing MMO games), and bought their first Macs specifically to try out the iPhone development program. The program was designed as a water simulator, and the koi were added later (as opposed to many of the devs we’ve heard from so far, these guys were actually concerned that their app was worth less than $1). And the little stories about feedback on the app are really interesting — apparently a therapist has used it with Alzheimer’s patients as a quick form of therapy.

Looking for some last second App Store deals? Here are some bargains that have been sent in by their developers.

SuperPong
Strictly speaking, SuperPong isn’t a “deal” so much as a “get it while you can”. The developer, Jazon Burnell has been C&D’d by Atari so if you want to buy SuperPong, you need to act quickly. SuperPong costs $2.99 until it is pulled from AppStore.

Fairway
Fairway, which normally retails for $10, will be selling for $4.99 for this weekend only. Check the price before you add it to the cart because it’s still showing up as $9.99 for me. Fairway is a golf management system. I suspect you’d have to know and love golf in order to appreciate this app. I am not a golfer.