Ultralisks tend to be more of a late game strategy usually combined with other units, not really the type of unit to max out on individually. Here's a couple replays, each one uses ultralisks but with a bit more of an emphasis on their other units.
http://www.youtube.com/watch?v=xQGUtasJtPQ --- My PSN: Khalisis
By far their most effective use is as a tech switch in my opinion. For example, you maxed on broods so the terran has a fleet of vikings and no marauders, so you suddenly roll him with ultras before their hard counters come out.
Obviously this doesnt happen a lot because it requires a game to go long enough to max, switch techand remax again, aka super late game. --- Still playing Brood War. |W|E|E|D| - My anti-drug.
having 2~ ultras under your broods to prevent stalkers from blinking underneath is really strong
otherwise, fairly useless.
in zvt you can make ultras to have a good % at finishing the game with your lead, bbut... that only works if the terran is dumb and doesn't understand where he is in the game. (ie: if he tries to push you while behind, or isn't being as defensive as he could be sieged tanks and bunkers.)
ultras are much like roaches, they are decent fighting units for a little while but if your opponent isnt stupid and isn't insanely far behind, then they become useless.
i think broods are better in all situations vs everything but insane amounts of spread vikings. --- http://i.imgur.com/U5y3b.jpg
I like to get them sometimes when I go linfestor and I know the terran is on 1-1 upgrades at that moment you can win the game with ultra's. Else I cant find a reason to make more then 1. ULTRALISK DROP HARRAS --- "It doesn't matter how many resources you have, if you don't know how to use them, they will never be enough"