Jumped in with both feet yesterday and bought the DC65 Animal Complete. Had actually skipped a week in vacuuming, so my first pass yesterday brought up a lot of dirt and dust, more than what's usual even with the DC07 (which picked up more than any of our previous vacuums).
Obviously if I'm willing to spend over $500 on a vacuum, I'm already a fan of the brand. So let me just focus my quick review on the improvements from going to the 07 to the 65.
[*]It's much lighter than the DC07 - this makes a big difference when doing the actual vacuuming, and moving around from room to room and task to task.
[*]The ball really does make a big maneuverability improvement. With the ball, the swiveling head, and the lighter weight, vacuuming was considerably easier. Usually I break a sweat with the DC07, but yesterday I finished without even breathing hard, and although I didn't time myself, it felt like I completed the task 20-30% faster. If you have a Dyson without the ball technology, and you're on the fence, get off of it and buy one with the ball tech.
[*]The newly redesigned head and brush, which goes almost all the way to the edge, does make cleaning the carpet closest to the walls and corners much easier, especially in comparison to the DC07. If you're anal retentive you'll still need the crevice attachment to get that last little bit. I'll do that probably once a month, but for a quick weekly vacuum I won't bother.
[*]The cord is much more heavy duty, and doesn't get as warm (especially at the plug) as the DC07 did.
[*]Not having to stoop down to change from carpet to bare floor: priceless.
[*]Separate button to stop bristles: priceless.
[*]Despite pulling up more dust and dirt from the carpet, it's around 30% quieter than the DC07 when running. I used to put in my in-ear-monitors to partially shut out the vacuum noise, now I don't feel the need to do that.
Now let me address the most common complaint I read on the web prior to purchasing: that the DC65 doesn't always lock in an upright position. I can say with mine that is not the case. But I think I understand why people get fooled into thinking they've locked it when in fact they haven't.
If you do not power on the vacuum, it's really easy to tell when it's locked in its vertical position. There is a definitive click and the vacuum will not bend at its swivel point anymore. There is only one position that results in the audible lock click sound, there isn't any other click, at a lesser angle, that can cause confusion as to whether it's locked or not. That's what some online reviewers contend.
However if you are using the vacuum and then you power it off, there's about a 5 second spin down where the vacuum engine is still going, but ramping down towards being off. While it's powering down, the vacuum is still sucking in air. If you then try to put the DC65 into the vertical position, it hits a point where the vacuum thinks you don't want the suction coming in from the swivel head, but rather from the handle (i.e. you are using accessory attachments at the handle end). This results in an audible "air pop" sound as the source of air intake switches from the bottom of the vacuum to the top of the handle. This pop happens before the DC65 is vertically locked (about 10-15 degrees before that point). This audible pop could be mistaken for the vertical position click, and that's when if you let go of the handle, it will crash to the floor.
Once you know the difference, it's really easy to tell when it's that air-pop sound versus the vertical lock click. One is a mechanical click sound, the other is an air popping sound. Or you can let the DC65 completely power down before putting the handle in the vertical position, and you'll only hear the click. But I tested this out many times yesterday, and I never made the mistake of having the handle fall to the floor.