As stated, the front spacers will cause excessive droop on the front suspension. You absolutely need to check the CV's for binding at full droop before you take off into the woods with it. (It'll be fine on the pavement).
The other problem with the front spacer lift is that at full compression the shock will likely bottom out before you hit the bump stop. This is hard on the shock and can cause failure if your driving style is such that you often bottom out hard. If you drive slowly over big bumps that won't be a problem.
That being said, I have the exact setup (from Daystar) that you are looking at on my '06 and I'm happy with it for my current use model. When the XREAS fails I'll slap some Bilsteins under it, but the spacer lift was a good way to get a feel for the lifted vehicle with a pretty small investment of time and money. Didn't affect the ride at all.