I've had the 951 for a while now and I really like how it works, but one thing kind of bugs me about it. The base unit connects to the soldering iron holder via a 1/8 inch phono type cable and I find it to be more of a hassle than either the main power cord or the iron cable itself. I like the sleep functionality but wish they used a similar concept as used in the various 858D hot air stations -- a magnet and reed switch. So, if the iron holder had a magnet and the iron handle had a reed switch then you could do away with the 1/8 inch phono cable altogether and that would make me really love the Hakko.
Another option would be the use of a hall effect sensor in the iron handle in place of the reed switch, but given the cost difference and the relatively low number of actuation's there should be little worry about a reed switch failure with use.
I have my 951 on a shelf just above my work bench/table and I leave the base unit there only moving the iron holder as needed. So, without the phono cable I'd have almost no hassling with wires/cables when moving the iron holder in and out of the rack and around my work table.
Brian