Let's not catastrophize things. The '81-up Slant-6 hydro lifter setup is unconventional, with its top-down oil feed, but it works well for plenty of years and miles, and doesn't cause problems. They pump up just fine, and fast enough—unless the vehicle owner uses too thick an oil, and/or is super neglectful (skips multiple oil changes in a row, etc).
The only real downside is the meek stock '81-up camshaft. Better cams for the hydro setup aren't off-the-shelf items, and buying the generic Chevrolet-lobes-on-everything crap from Comp can make you cry, but a good cam grinder (Oregon Cam, like such as) can make a fine upgrade cam.