I play-tested the new WH40K 8th edition rules with my friend Curtis Turner (Hostile Contact) this afternoon at my house. We got a 1500 point game done in 1.5 hours.
Here are my impressions:
1) Vehicles are harder to kill in the new edition. Vehicles have Strength, Toughness, and Wounds stats. It simplifies the game instead of dealing with armor values. However, land raiders are tougher to kill outright. I crippled a Chaos Predator with a couple turns of turns of las-cannon fire from a Deathwing Land Raider. Both my Land Raiders were standing at the end of the game.
2) Close combat and power weapons maul Space Marines in regular power armor. Terminators will last longer in close combat for a couple of turns. However, regular marines (both Chaos and Imperial) are more fragile to outright effects of power weapons.
3) Psychic powers can be effective if your opponent doesn't has a psycher. They can't counter your psychic power plays without a Deny the Witch roll.
4) Storm Bolter rapid fire can be effective in removing regular Space Marines. Assault Cannons are also effective in clearing out troop formations, too.
5) Deathwing Terminator armies are more effective in this new edition of WH40K. My termis had more staying power with two wounds than previous games.
6) Curtis had horrible dice rolls. Mine were good (for a change). I didn't know what happened to my usual luck. I'm not complaining. I won this game we played. I was destined to lose when Brian Bigford blew up one of my land raiders on Turn 2 the other weekend we gamed...
Overall, recommend edition. Plays faster, bloodier, more tactically forgiving.