I've had five really nice cards so far, but haven't commented yet, so here goes:
piu58 - "Carline Thistle" - Looking at this card, you can feel the cold. And the old paper gives it a classic tone.
Ed Bray - "GWR Pannier Tank 6430 & Autocoach W225 - An interesting subject, printed well
Peter Schrager - "Backlot in Las Vegas" - The collection/selection of complementary shapes makes this for me.
redrockcoulee - "Weathered Pillars" - A very nice use of tones and repetition
Trond - "Shore" - Lovely repeating ripples and surrounding textures. The wide borders really suit this.
That's five down, and nineteen to go. Thanks everyone for participating.
PS Just one request to those who haven't sent their cards out yet. It really helps those of us who are slightly disorganized if you include the postcard exchange round number, your name and a title.