Is 100% Private Label important for reseller services?
Not many companies offer it for their customers but I'd prefer to have.
Say sharkspace.com specify this feature in their plans and it's quite clear that anyone may have it.

The greater part of hosting companies (resellerzoom.com, webhostingbuzz.com, etc.) that provide reseller services, offer that feature for their clients. I don't think that it's something new and unique.

Sibername.com offers that feature in their reseller plans.
That company has many reseller-friendly features with one free domain name and excellent in-house support.

Reseller accounts from MMhosting.com provides these features too.
reseller accounts are completely transparent in every aspect allowing each reseller to fulfill their services without the worry of being discovered as a reseller.

This company is good, but I suggest you to look at Glowhost.com reseller offers. I have found out that it offers affordable price for its reseller plans. Their services are widely represented in the web hosting market.