Listen to my personal experience (not what people say on travel blogs):

My KLR's (KL650C as well as KL650A) do between 60000 and 75000 km before they need a rebore / OS piston and valve / seat remachine. They do the majority of mileage on dirt roads and are often heavily packed and travel two up. They have to endure the odd idiot on the controls. I own / owned 8 KLR's all together and am still servicing a few of the bikes that were sold before I took over Le Cap. One privately owned KLR is on 95000km and still runs fine. It got a new balancer chain at 92000 as the old one was stretched and the idler would not take up the slack any more.

Mechanical engine failures so far:
Various broken balancer chain idler levers (=doohickeys) and lever springs. This typically occurs after some 30000 km. It is very easily recognizable, cheap and easy to fix and has not caused any further problems on my bikes. The broken idler lever or spring only cause severe damage if the problem is left unattended for a long time as it causes the chain and chain guides to wear excessively and eventually to fail.
Water pump shaft seals: The water seal on one bike started leaking just before the engine needed an overhaul.
One massive gearbox problem. The dogs sheared off one of the gears and damaged a neighbouring gear as they got ingested. I have never seen or heard of a similar problem on a KLR.
Electrical failures:
One alternator developed an earth leakage under load (KL 650A 18 months old). Fixed by rewinding the stator.
Failures on frame / suspensions / wheels / brakes: Nil. Not even a single snapped spoke.

I wonder where you get the information about the new (2008 model although it will be available in 2007) KLR's new engine from? According to my information the cams and ignition system have been modified. The engine is still the same.

If you want to go fast you should get yourself a R1 or a 'Busa.