I used to ride a Demo 8 and swapped only because the frame was a tad bit too small for me. If it weren't for that, I'd be keeping it.
Pros:
- Frame is built really well, welds are fantastic
- Anodizing on the 06 Demos are hard wearing, they barely mark. It's so resilient to scratches.
- Adjustable geo means you can set up the head angle and bottom bracket height depending on what kind of trails you are riding.
- The demo 8 can plow through rock gardens
- No brake jack
- Rides a lot lighter than it is
- Pedals well for a big bike
- Smaller BB width means you can run XT cranks
Cons:
- Adjusting the rear shock is slightly inconvenient due to the position. However, I'm the kinda person who sets and forgets so only found this an issue once a year if that
- My frame weighs 5.3kg with shock, seat clamp, dérailleur hanger
- Tis annoying to clean cuz of all the nooks and crannies. However, if you use muc off then it is irrelevant. Not really a con though, I'm just lazy
I definitely LOVED the Demo 8. Prior to owning that I had a Giant DH Comp which I thought was the business, but this bike is miles ahead. It's a very confidence inspiring bike that's for sure, and it's definitely progressed my riding a heap.
If you can pick one up cheap I say go for it, it guns like a champion.
My only advice, don't go for anything before 06 as they had issues with cracking.