I would distinguish between the total amount of time that combat takes and the amount of time that each individual player takes for his turn.
I think that 4E changes such as reducing the number of options available to spellcasters and requiring PCs to share actions with their mounts, companions and summoned creatures was an attempt to reduce the time taken by individual players on their turn. I might have made an argument here that 4E could have increased the time taken by melee characters on their turns since the number of options they have been given has increased, but
it has been pointed out that melee characters actually had more options in 3E since they are no longer able to trip, sunder, disarm or overrun in 4E without selecting specific powers. Hence, melee characters should also take less time on their turns than they did in 3E.
It sounds good in theory, but I don't think it bears out when actually playing
4E. In 3.0/3.5 melee types could do special manuevers, but rarely did unless they were built specifically to be good at them. They were ususally too suboptimal to bother with. The only time melee PC's ate up a lot of time was when they had a bunch of attacks via two-weapon fighting. Usually they would just full attack. In 4E, more classes than ever have more options to pick from which takes a decent amount of time for players to sort through to pick what they want to do. They have to decide on what power they want to use, whether to use an action point, how many enemies thaey can catch wiith a blast, etc. They also usually look to see if there is something to do with their minor action. If they have bursts, blasts, or multiple attacks (which quite a few 4E PC's do) they start to eat up as much time as two-weapon fighting specialists in 3.0/3.5 to resolve their attacks. They also have to deal with tracking more conditions than they did in 3.0/3.5. All of this adds up to rounds taking as long or longer than 3.0/3.5 rounds, but since it takes more rounds to kill the creatures (thanks to a hit point/damage ratio that heavily favors the monsters) the combat just ends up taking longer.