esd safe isn't all that important for generic soldering but if you plan on reworking anything with ic's eeproms etc. ever it's not a bad idea infact I wouln't buy one thayt wasn't just because it doesn't cost anymore that non esd and why chance it or why have to buy anothein the future... I have the 921zx and wes51 and a portasol all are esd... infact I want to sell the 921zx like new condtion W/ 5 tips and a spare heating element 75$ if anyone here is interested...meetoo[at]fastermail[dot]com (tips are about $10 ea. and element is about $20...)
I also understand staic can collect near the tip because of the dry air present from the heat...