Are there any negitives?

You can get light primer strikes; some folks seem to have a real problem with this, others none at all.  I don't know if this has to do with how aggressively you follow the instructions, the makeup of your original springs, the phase of the moon or what but I'm very please with how the D.I.Y. Trigger Job smoothed out the trigger pull on my Bushmaster.  I expect I get maybe 3 FTFs out of 500 rounds of XM193 but when that happens I do an immediate action drill and keep on going.

Anyone else?

Ditto.

I was a big fan.  Shot 1000's of rounds.... and loved this trigger job.  And for a bench rifle, plinker, etc... it's still the cats meow.  

That being said... light strikes is a negative on a "social" rifle.  I shot a lot of Q3131A without issue, then one day, in a class, with a rifle that had been 100% with the 15 minute trigger job... I got several light strikes on each mag.  I assume this was a lot of Q3131A with slightly harder primers.... but in any case, a light strike on commercial factory ammo.  I have since switched to the RRA 2-stages on my more serious or more shot rifles.

I still would not hesitate to do this.... if you arent happy with the results, two springs are all its gonna cost ya to go back to factory.