I read about this on 43 Rumors and my first response was to post this on the Fun with Panasonic GH3 thread.

I decided that other users of Micro Four Thirds cameras might want to try out both the Panasonic GH3 and 12-35mm f/2.8 lens.

As an OM-D EM-5 owner I would like to try the Panasonic 12-35 f2.8. I would also like to try the GH3, but not as much as the lens.
I would be more apt to buy the 12-35mm f/2.8 lens than the GH3 if I was going to spend another $1000 plus on photography gear.

If anyone does the test drive, let us know what you think.
Just remember that Panasonic's goal is to separate a photographer from his or her money.

Smart: Panasonic ‘Try Before You Buy’ Service in UK! | 43 Rumors
Panasonic UK just had the smart idea to launch the new ‘Try Before You Buy” servie! Basically you can get the new Panasonic GH3 and 12-35mm lens for 48 hours (excluding delivery and collection time). You will have to request he camera form one of the stores listed here below. I think that’s a great thing for all those of us that want to try a camera before to actually buy it. Barney Sykes, Lumix G Camera Product & Marketing Manager says “The GH3 is by far the most advanced system camera we have ever launched and we recognise customers may want to road test this product before committing to such as high value purchase, therefore we are delighted to be able to offer this scheme to our key retail partners to help increase their sales opportunities”

I wish this service to be extended worldwide!

Retailers include:

Annings, Ilkley, Yorkshire
Bradford CE
Camerabox Kettering
Cameraland / Stanbrook Cardiff
Camera Solutions
Carmarthen Camera Centre, Camarthan
Castle Cameras Bournemouth
Chas Eagles
Chas Norman Cameras Sevenoaks
Chris Goodhead
Clifton Cameras Dursley
Frank Wilkinsons
Harrison Cameras
Mifsuds Brixham
Park Cameras
Peter Rogers
Photo Express
Photosound Vantage, Bishops Stortford
Richards (Bass & Bligh)
S R S Microsystems Ltd Watford
T4 Cameras Swindon
York Camera Mart
Conns Camera, Ireland
Bermingham Camera, Ireland

found via Whatdigitalcamera - Panasonic offers a ‘Try Before You Buy' Service | What Digital Camera