I’m always on the look out for a new OS, especially one that is designed from scratch to be media savvy, fast and attractive. There is some very tough competition out there and having had one look the desktop design is a miss. The flaps on top of the window which look like they are there to mimic file tabs are unattractive. I’d love to see the desktop receive some beautification!
Beauty is subjective. IMHO the minimalist “90’s” feel of Haiku is very pleasant to me, much more than XP’s Luna or Windows 8’s desktop interface. I’ll admit there are prettier interfaces out there, but for a FOSS OS, Haiku has a very nice consistent interface, something many linux distros lack. Also, the tabs become something much more unique when you start to use stack-and-tile, making application interaction simple and powerful. I’ve never seen window management done better on any other OS, even in S&T’s unpolished state.
Dunno if I’d consider Haiku as “designed from scratch” as it started out as a reimplementation of beos, but I could be wrong about that since (to my knowledge) it really was built up from scratch.
As for competition, personally I don’t think Haiku is a direct competitor for Linux or BSD, at least not yet :))) Both of those have a long, long history of development behind them and are miles ahead of Haiku for that reason alone, but personally I find that Haiku has matured to a point where it’s usable enough to use daily for simple things–but certainly not a desktop replacement yet~
Also, “one look” isn’t enough to get into the Haiku UI, which is designed to be minimal and easy to use, both of which have been achieved.
The reason “one look” isn’t enough is because a lot of parts about it can easily be configured. It took me about 20 minutes to get to a fairly attractive desktop (although prettiness is subjective, of course). For example, if you don’t like where the deskbar is, you can change it so that it looks like a long bar across the screen like what you usually see on Windows or Linux.
Another thing you can do is change the colors of the deskbar, the menus, the file browser. . . It really is a breeze to configure 
Check the preferences–I should probably also mention that the file browser can be changed into something more familiar, but I took the User Guide’s recommendation and tried to get used to the defaults at first. As a result, within a week I was using it instinctively and I’ve found it quite intuitive. Even the deskbar is at it’s default place in the top right corner.
Of course, your mileage may vary on all of this
As for the tabs, I didn’t like them at first, but they grew on me. I don’t know if they can be changed, but if they couldn’t I wouldn’t because it’s part of one of my favorite things about Haiku’s windows management, which is the stack and tile feature.
A temporary measure is to press the fullscreen shortcut keys, as the tabs will disappear–but that is only for one window.
To be honest, I had a few gripes about the UI at first, but after a few weeks of use they are almost all gone I use it almost daily for school and haven’t had a problem with it as far as usability and aesthetics go~
Anyway, I hope you give it a chance Maybe when Haiku has more releases behind it and has more developers, there can be alternative choices for UI, but for now I don’t think it’s a priority.
Also, I have to mention: Haiku’s UI, to me, is wonderful because it is, hands down, the most transparent I’ve ever seen. Most things that you need to find is probably exactly where you think it will be. It’s amazingly refreshing because Linux can be pretty convoluted
Okay, sorry for rambling I’ve only been using it for a relatively short time, but I am quite pleased with it, thus the long post
I quite like the minimal look of Haiku and I hope it doesn’t end up all bells and whistles like windows, its so fast and I’d prefer it to stay that way and useable that have loads of useless animations
My beef, is every time someone suggests making the UI prettier that they never explain how these extra work will benefit the users (ie. people like me).
What use are extra effects that will cost the developers time and effort if you can’t show an improvement beyond looks? Some appearance improvements can speed up user interactions, but most times I just seen useless pretty fluff being asked for.
Please, all you UI designers out there, think of things that are real advances to the human <-> computer interface instead of following the fashions of the day.
The “flaps”, as you call them, originally annoyed me when I first started using BeOS. I’d switch the decor to the AmigaOS design because it created smaller, less intrusive title bars. And for that matter, I’d still like to see slightly smaller title bars in Haiku–it doesn’t necessarily have to be like the AmigaOS, just smaller. Perhaps the size of the title bars could be made adjustable (just as I’d like to see adjustable border sizes)? Then each user could adjust the title bars to their own preference.
There are some minor things that could probably be modified to “beautify” the interface without affecting its usability, but overall, I would say that fancy designs may look nice, but tend to make the user experience harder, not easier.