As indicated, the repair (collarless) studs are nowhere near as strong as the shouldered studs in terms of resistance to deflection. They will still be a lot better than the pressed studs for resistance to pull-out, however.
If you want a quick/dirty fix to lifting studs, the collarless type will work. If you are building heads and want to do it correctly, get shouldered studs, remove the heads, and mill the stud bosses flat. I've done both and had no problems. For a very aggressive cam and set of springs, the collarless type may not be up to the task. For a relatively mild street application and cam swap where you might not necessarily want to pull the heads, they are superior to pressed studs.
From my experience, if you plan to use floating rocker arms and guide plates, the stud bosses should be milled down about 0.400" from the theoretical deck, as ede explained. If you are not intending to use guide plates, you can mill about 0.260". I've had very good success using a piloted spot face cutter. You can jig the head level then whip out all eight holes in about five minutes.
An easy way to determine the deck is to measure the height of the existing studs as a reference for final depth. | 
