I've had a quick play of it but first impressions are pretty obvious: They've done a magnificent job. So many tiny little improvements all over the place, many very subtle.
For Heretic, many of the gameplay tweaks seem to be informed very much by the Heretic mod "The Wayfarer's Tome" which rebalances the game in many subtle ways to make it much more fun and less grindy.
And for Hexen, you can just look at your map to see where you need to go next and the main hubs are given more visual clues as to how you're progressing and what is still outstanding. And little things that'd shit you to tears - the mage's ice shards can pass through frozen enemies so their statues don't bog down the fights anymore and centaurs/slaughtaurs no longer are guaranteed to turn into invincible turtles every time you hit them - they don't raise their shields as often and when they do, you can get around from behind!!
It's quite evident they've paid great attention and have had a finger on the community pulse for a while to smooth over some of the welts in the original games that they were criticised for, even when they first came out.
