Universal binaries? These apps don't need no stinking universal binaries! That is, the following three apps are not tuned for iPads. A universal binary will switch to the "iPad version" of the app for that device. So you might have MobileStudio on your iPhone, but it also looks great on the iPad because they wrote code and added graphics to accommodate the larger screen size. But the apps I'll list look great with just the 2x upscaling you can do with any iPhone app (like, say, Apple's own Remote app, which is kinda lame on the iPad).
1. Bebot. Now, I've loved Bebot since the day I kissed his cute metal lips. But as a true instrument? The tiny screen on my iPhone did OK, but the iPad allows Bebot to really become a workable synthesizer. Not only that, but those chunky 50's-inspired graphics scale exceptionally well. No need for enhancements, although the tools for customizing Bebot's noises could use an overhaul. How about flip the screen ala iBooks and create a Moog-like patch panel for making new sounds? Analog heaven!
2. Scanner911. OK, so the aliased text on lists and most text IS there. That part doesn't scale. But when the scanner is actually running it looks like a big ol' scanner from something like BJ and the Bear. I want to mount the iPad on some dark wallboard and put an ashtray in front of it for guests. Scanner911 is one of my favorite apps, and I dig that somehow their graphics hold up when doubled.
3. World of Tunes. Most of the tap-based music games on iPhone are too cramped for my arthritic hands. But expanded twice their size they become enjoyable pastimes. World of Tunes is not only more fun on a bigger screen, it allows others to watch (and get those damn songs stuck in their heads). Plus the graphics look kinda cool and retro. The chunky graphics and gradients remind me of hours of playing Sonic. My kids certainly seem to enjoy the game as it is (for now) their favorite on the iPad. It's a really fun, cute game and quite a deal at US$.99.
I have close to 2,000 apps on my machine but have only tested a fraction -- so let me know in the comments what apps you have found that look great when simply doubled. It's also possible that at any time the developers of these apps could push an update that adds scaled-up iPad versions, but for now they rock without update.