Personally I've found it a bit easier. In 4e, it's very difficult for a character to have the ability to use the same daily twice per day, or the same encounter power more than once per encounter. In 3x, you can prepare 3 of one spell, 2 of another, etc ... so, it's harder to remember if all of that spell has been cast than a simple "did or didn't he". It may be because we haven't reached 9 yet, but it hasn't come up. Sometimes there is trouble remembering between sessions what has or hasn't been used, but that can just as easily apply to spellcasters in earlier editions. The way most of the fights go, it's easy to remember if certain dailies were used. It's hard to forget when a sleep hit, or a lead the attack ... although some of the "simpler" dailies might be forgotten, like Brute Strike. Often the adventuring day ends because of healing surges [which are arguably tougher to keep track of ... you have to trust them to take the right damage, including ongoing damage, and when they spend them, track the surges, etc, etc, etc].
There are some tracking issues of trust ... I've been playing a warlock in one campaign, and the DM basically has to trust me in that my defenses will rarely be the same two turns in a row, as sometimes I have concealment, sometimes I'll have the benefit of second wind, sometimes I'll have the benefit of my utility power to teleport and get bonuses to defense, sometimes the attacker is marked, and I'm a halfling which boosts my AC against OAs, etc.
