IN general, the LML powered GM trucks are a great platform. Modern day power bone stock (or close anyway, lol), transmission that was the benchmark for 10+ years and as good of chassis as any truck on the road.
The couple concerns (same as any diesel truck) is it was first year for the new emissions systems. The folks I know who have them haven't been extremely problematic, bout the same as any of the big 3. If you're in an area With no emissions inspection, then this is a $1500 fix to permanently fix all emissions issues. If not, it may cost some $ down the road. Again no different than the other 2 mfgs.
CP4 pump may be a concern. More so out of warranty. You can gamble the low odds that it will fail (but high odds it'll take out the whole fuel system if it does), retrofit a new CP4 blocker plate to it, or replace it with a venerable CP3 pump relatively economically.