Woah! I had a load of entries for this competition - thanks for everyone who emailed in - it was great reading all your opinions and there were a few humorous ones too :-)

It seemed that Aero was one of the most popular features, along with ReadyBoost and search - which is similar to what I like about Vista.

So the winner is.... drum roll...... Robert Banghart who captures the speed and impact of search in this succinct entry:

Search.

Need to find something to become productive.

Begin typing keyword(s).

Find.

Begin productivity.

People-Ready!

Dead simple.

Well done, Robert, the Vista USB Pen is on its way to you!

Some of the other great entries I received are here:

“Vista is fluid and responsive. Windows appear and disappear with panache and elegance. The desolate chasm between application and operating system has been turned into a beautiful prairie.  In short.” - Clifton Griffin

My favorite feature is that renaming files in explorer no longer select the file’s extension. It’s a perfect example of how minor changes can have a big impact. - Timothy Verheecke

Superfetch is my favorite feature in Vista,really cool,i mean imagine having apps that are
precached and those that negate the negative impact of apps running in background like anti-virus etc. - Rajesh Ravikumar

I love the search functionality!  You don’t need run to do cmd. Just type cmd or  if you want to go to add /remove then ‘remove program’ and there you are! - Alpesh Nakar

.net 3.0 is my feature of choice.  It’s so great because of the applications that will be built upon it. Using Expressions the future looks cool. - Mark Brewer

The taskbar previews are great because they allow you to look at all the open windows without restoring them from the taskbar. - Bryan Pollack

Live taskbar thumbnails, of course! :-) It speeds up working with many windows of the same program (i hate grouping icons in taskbar). - Aleksionas Greatest

A new TCP stack that automatically optimizes itself based on your connection speed. - Marc Merritt

DirectX 10: WDDM and DirectX 10 will provide a much more powerful platform for game developers, as well as Aero and WPF - Jonathon Rossi

I am a 16 year old student that lives in the UK my favorite feature of Windows Vista is the side bar because it allows me to have all the photos of my family from faraway places whenever i want. I might not sound much me it means a lot to me. - James Weston

My favourite Vista feature is Speech Recognition. Even though the tutorial is long, it works really well and better than any other speech product I have used before. - Sanchay Ladwa

the Bitlocker Drive Encryption,New Installation System,Aero Desktop,UAC,Session seperation for processes,User mode drivers,Windows Meeting Space.
I love all these bcoz of the innovation of the features from Microsoft with Vista. - G Krishnaa

Aero. Easily the best looking desktop I've ever used. Apple's 'Aqua' looks like a toy compared to Aero. - Frank Becker

The best feature in Windows Vista is the Flip 3D, because you can show your friends who don’t know anything about computers how cool the new Windows is - Krister Monsvik

If only everything in life was as reliable as Windows ReadyBoost, my life would be a lot easier - Michael van Goethem

As an audio enthusiast the new audio capabilities have got me litarally drooling. Easier configuration, audio enhancements, less latency, higher quality. It just sounds (pun intended) so friggin' awesome :D - Stefán Jökull Sigurðarson

I think my choice would have to be the Sidebar. In my humble opinion, the Sidebar brings the possibility of realization of the concept of “Information At Your Fingertips” - Scott Kindorf

Vista's deployment methods using WIM for deployment should prove to be a great feature in corporate environments, I can't wait to start deploying it in our organization - Christian Mohn

My favorite is Search, the work done around Search and especially the way it was implemented (start menu & explorer) on Vista will definitely make my windows key wear out - Luís Abreu

Windows Photo Gallery integrates much-needed photo-organizing capabilities to Vista. People will be much happier when their photos are neatly organized as opposed to just randomly floating around their hard drive - Jason He

In Vista, personally I save about 3 seconds each time when I use start menu to find a program. That alone saves me about 6 hours a year (avg of 20 times a day). And I could earn twice the price of Vista in that 6 hours - Jebaseelan Joseph

So easy to use, simply press the windows key and all your programs and documents are just a few key strokes away. Simple, fast and practical - Daniel Murfin

Thanks again to everyone who entered - nice work!