[Chazar]

Yes! Two examples, followed by a big but:

• A Hill Fortress proved to be an excellent idea when I played C'tis Miasma for the first time:
  It took Ulm quite some time to breach the walls despite bringing a few sappers (but still too few compared to the Ctis City Guards). So the Ulmish knights retreated, collected more sappers and returned, but still the siege took 3 turns. The Ulmish siege was also faught back, since their precious knights were stuck in the narrow passage blocked by undead chaff. A couple of poison slingers dealt damage to them. The two ulmish earth kings (equipped as combatants and not as caster) flew inside thanks to their symphalian wings, but got quickly disposed by my opposition casting shamen communion.
  
  So a couple of city guards, two marshmasters and 5 or 6 shamen hold back a large number of ulmish knights, 5 smiths and two earth kings! Of course, quite a few knights survived the poison damage and retreated - but being diseased prohibits healing, so those units were doomed! All 5 smiths were also diseased at the time of battle!
  
• As Caelum, I usually take the WizardTower. Caelians are hungry, so quickly building a high admin castle is important to yield enough supply over some distance to prevent starving. (BTW, its a pity that again the all-important admin score is used, and that the supply-score is not even a factor for distance feeding!) My Caelian armies are hence usually followed by a trail of Wizard Towers. I agree that for merely pumping out Caelian Wizards, a WizardTower is a poor choice compared to Watchtowers, since on may afford more WatchTowers+Wizards than WizardTowers+Wizards...
  
• However, I usually play short crowded games which are already finished by turn 60! Like 7 players on inland with only a couple of victory points. Most of our games are even decided earlier, around turn 40ish (guessing). I am convinced that the time of castles is over, as soon as national troops have become obsolete!!! Well, SCs and excessive Magic is natuarlly worse than gunpowder!