Summary: I needed a ballhead to be able to do panoramics in the field, but didn't want to break the bank. I have serveral other heads, but none are ballheads so they are somewhat clumsy. This head instantly made all of the others feel useless. It is very smooth, and easy to lock rock solid with only a minimal twist. I had planned to also test it with a 600mm f4 and TC on it, but did not have a chance to use anything longer than the 80-400 VR.
Summary: This ballhead is perfect for use in combination with Neotec monopod, and probably others as well. The fine adjustment of which this head is capable makes handling of my Canon 5D/70-200 f2.8 combo 'feather-weight' operation. This combo allows for more natural camera/lens grip while on monopod (or tripod); for me it's a great improvement over Manfrotto's 322RC2 ballhead that I've used for two years prior to acquiring the hydrostatic unit.
Summary: This is really nice Ballhead. It works wonderfully. Small light turn and the head is just solid like a stonehenge. However, it lacks of expensive fancy built looks like RRS. It holds 300mm f2.8 VR plus TC, and D300 with MBD10 grip rock steady, yet easy to unlock.
Summary: I already have a non Hydrostatic ball head from Manfrotto and I couldn´t note (yet) any significant difference between them. I think one must prove the two models (Hydrostatic and non Hydrostatic) before buy. It´s a good head, very light, well made, etc, but I don´t know if worths the many more dollars.
Summary: I use this primarily with a canon 100mm macro lens, a 24-70mm and a 70-300mm zoom. The thing that is amazing about this compared with my old Manfrotto head is how smooth it moves and what little effort it takes to lock the camera into place. A gentle quarter turn and the camera is locked!
Pros: Easy to use, Improves Tripod Function, Intuitive
Summary: At first I was hesitant to pay this much for a ball head, but within 1 minute of attaching my 30D w/300 F4 IS to it, I was convinced it was worth every penny. My previous ball head, the 486RC2 was so hard to lock down, almost got tendonitis. This hydrostatic ball head requires just a small turn, without breaking my fingers. Once it's locked, IT'S LOCKED. I no longer feel like I'm going to "strip out" the locking mechanism.