Wow - I can't believe I missed this thread.
Windshield decals - depending on the car and outward visibility, I think they're pretty cool.
With my first Mustang, back in the late '80s, I started with one of those static cling decals... and it promptly blew off at-speed on my first drive from New Mexico to Utah when I went on leave. After that, I decided on something more 'permanent.' I used some of the adhesive "fade" body trim to make a big stripe all the way across the windshield, then cut-out the graphic I wanted. These letters were the same as the cheesy decal that came with the nose-bra I'd bought for it. Driving into the sun, they were actually helpful in diffusing the direct sunlight on several occasions.
My next vehicle, I did the same thing with some simple block-style letters spelling out "NISSAN," with a little twist. Made it easy to duplicate, since all the mud and use of the windshield wipers would eventually erode the color after time.
On my Jeep, we have a decal from my favorite Off-Road shop from Salt Lake City, Utah, Mister 4x4. That sticker also inspired my first e-mail address, as well as all my forum screen names since the mid-'90s.
That sticker is a major PITA to see around, BTW. I'm surprised the state vehicle safety inspector keeps passing it year after year considering how much visibility it gives up.
Aside from the Jeep, I think I'm pretty much over the windshield decal look... I don't think I'll be putting one on Frank's windshield.