Jim,
Seadeck does look great
what is shown there for SeaDeck is about $2k worth of SeaDeck for a DIY installed kit (I am estimating the swim platform) for a total installed surface of about 95 square feet, unless the costs have come down significantly recently.
Most boaters that want to get away from carpet (about $300-600 installed cost) and are viewing the vinyl as a cheap alternative when they get sticker shock
besides seadeck other choices are Flexiteek (not really that good), Nuteak, Marinedeck, Plasdeck, Atlanteek, Permateek, Plasteek, Aqua marine deck, Estec, Herculan, and a few others that have popped up.
At worke have used Estec on a few gangways, and while you can do funky patterns and colors, its only available professionally installed (outside the reach for most boatman's pocket books)
The same surface sprayed with Line-X XS650 would be about $1000-1500, however it would be impervious to fish hooks, fish knives, etc. and give you wet traction.
There is always the DIY non-skid surfaces which can be hit or miss. the durabak product has failed on boats as well as trucks - wouldnt recommend it. Monstaliner is another that I am not sure how it would hold up. Raptor liner doesnt build to the same thickness as the professionally sprayed polyurea products, however they do provide the gun with the kits and the kits are available in white and light grey. they are specifically listing marine applications.