Worth upgrading?

To the retailer, yes. To you, no.

And some day, those will be great reasons to update. But there's no reason to replace a working modem today.

By the time the day comes that there will be any benefit received from updating, the SB51xx may already be obsolete as well. Spending money now to replace the SB4100, which isn't yet obsolete, and is still working, is just a waste of money.

Now if you were talking about an SB3100 or SB2100, or an SB4100 that was damaged, the story would be different. But there's no need to replace a working modem that's not yet obsolete with a newer modem if the features of the newer modem do not yet offer any benefit.

Buying technology products in advance of their need simply doesn't pay for the consumer.

on the contrary;

The SB51xx series have better hardware to support BVI, Voice, DOCSIS1.1 QoS.. Some MSO's are forcing a tighter security measure and may require the additional hardware functionality of the later hardware; hence the reason they lease their units.

The only problem I found is that the SB4100 would not do the new Comcast speeds - 6 mbps - Silver , or 8 mbps - Gold. It was topping out at 5 mbps.

Some people / areas have this working, where other people / other areas could not. This has been discussed / documented in the Comcast Forums (in the

That may be so, but I don't think that this is a factor for the original poster as he was using the same modem and getting 10 mbps.

Understood - my point was that the modem may perform differently with a different ISP / network ...

What you say is very true...and sorry I missed your intended point.