eNom has grown from 1M names to 1.2M names in just a few months. It is because of their wide reseller base and decent reseller prices. I also think its because they rapidly develop new products/services to sell.
Here are your answers:
Who is enom?
ICANN accredited domain name registration registrar.
Where is enom headquartered?
Redmond, WA (about two blocks from Microsoft)
What is enom?
See above. BTW, nom is french for name.
Are they currently the cheapest or easiest, or what?
yes
Why are they getting so many regs./transfers?
see above
Are they openSRS?
no. OpenSRS is a competitor.
Do they do online transfers fast?
yes
What is their niche?
good reseller tools and price with lots of bundled domain related services (real time DNS etc)
Do they sell direct?
to who?
Who are some eNOM registrars/resellers?
eNom hosts several other ICANN accredited registrars (that is provides the back end services). Not sure who though.
Why are so many people switching to them?
see above
Where is enom? What is their web address?
http://www.enom.com
servers are in Redmond, WA