We replaced our wood deck with trex 2 summers ago.
The Good: 1. Love the lack of maintainence!!!! We hated staining the wood deck, and thus, we'd let it go longer than we should have and it would look crappy.
2. There are a lot of design/color/railing options. We "picture framed" our deck with a darker color along the edge, and it looks beautiful.
3. Splinter-less. Love how smooth everything is.
The Bad: 1. Price. We used Trex brand, and the price is definitely much higher than a wood deck. There are cheaper composite brands, but after looking around we opted for Trex.
2. Ours does get hot in the summer sun. Luckily, our deck is only in the sun in the morning, so it's not too bad.
3. It also gets slick in the rain and I discovered this winter that ice forms a lot easier too. Crocks + rain or ice = me on my butt.

I think I'm still adjusting after years of walking out there on the wooden deck without so much as thinking about the rain.