I tend not to do tac boots anymore, though they are still good post-nerf. My first pair of boots will usually be A-modded Steel, assuming drops cooperate and the CC+ wasn't an absolute disaster. Later on, I try to upgrade to "army boots" (Protective+A mod) or "blue army boots" (Plasteel+A mod). Why? I like the extra knockback resistance, and because I like to have a clear path to Antigrav boots if I have the incredibly good fortune to find a nano mod.
As far as interesting interactions are concerned:
*Acid-proof boots are absolutely hilarious for flood levels and/or if you have the Acid Spitter. However, they will NEVER offer fire resist, no matter how many P-mods you jam onto them. Dunno about assemblies.
*AT Phaseshift boots are hella good. Just a T-mod pretty much negates the knockback penalty.
*Not a big fan of Gothic Boots- they're just too heavy. That said, somebody might have some interesting assemblies to build around them.
*Enviroboots/ Cerberus boots don't really shine unless you have the Lava Armor. I had an Ao100 game with Cerb Boots, the Lava Armor, and a Nanomachine Rocket Launcher. 'Nuff said.