I respectfully disagree. I still use partitions for several reasons on all my DAWs.
1) Multiple boot partitions. I use a program called BootIt NG to boot all my DAWs, and keep a virgin boot partition available for testing/sandboxing plugins and apps, and in some cases a Vista x64 boot partition or even Linux boot partition, that remain totally hidden during normal use, but I can boot into those as needed, and it works perfectly, and transparently, as if I had another computer. BootIt NG allows me to sandbox an OS and all the other hard drives into profiles of exactly the configurations I want to be visible to the booted OS. This incredible flexibility and control within a boot manager like BootIt NG make it worth it alone. Hands down for me.
2) To physically separate data on the hard drives for ease of drive imaging and backup. I keep many of my large hard drives ( 500GB and up) partitioned into two sections based on content. This helps me speed up complete drive imaging and backup procedures so I can deal with one partition at a time, instead of the entire drive. Saves me time and hassle I can measure when I do backups. Also, makes it worth it alone for me.
3) The above 2 reasons are enough for me, by far, but there are also minor security gains in terms of hard drive failure problems. In the past I have had major hard drive failures, and this is nothing I wish on anyone. Depending on the hard drive failure type, you can gain a little additional safety in the case when a hard drive head crashes within one physical partition, I am often able to recover more easily the content from the other partition. Again, this is a very minor benefit, and not usually worth mentioning, except it has paid off for me before. Obviously, you should be backing up regularly, so see #2 above for slight advantage there.
4) Helps keep fragmentation under control a bit more, and thus saves time and increases performance just for maintenance purposes. Since the partitions are separate, if you have a lot of activity in one partition, but not another, then defragmenting a hard drive will go much faster, since you can do this a partition at a time, not the whole drive.
5) Finally, there is a slight, but measurable performance benefit in some cases. If you INTELLIGENTLY organize which data goes on which partition, then you can reap lower access times and slightly higher data rates from one of the partitions. I don't need to explain the way hard drives are designed (which is quite interesting if you care to learn how cylinders/sectors are organized and how the drive head(s) work) making the early cylinders much faster. It also reduces average seek time in both partitions IF you stick to using one partition at a time. You don't have to understand the basic engineering behind it, you can just run a hard drive benchmark and you'll see.
I also believe it's just fine to leave it as one big partition if you want to -- I'm not dissing anyone who chooses to do that -- but all the reasons above make it worth it to me to continue to do it, and it has never been a negative... only a positive. You just have to understand how to best take advantage of it.