ISP Situation- Cable

I have a new Pentium D 945 with 2GB RAM and a 300 GB HD
Intel MB with XP MC

I upgraded my cable service to the best they had 10mbps +.
After I had the upgrade I'm still at high 3-low 4 mbps.
They came out and checked everything over as they had before. Its perfect- Computer and modem are new-cables inside and out,

So later in the day they sent out a guy to check the speed. He brings in a 4 year old Dell laptop- his words, Keyword is old.

Well that's the test bed. He hooks it up to my terminal- ( modem etc) and it pulls an incredible 15 mbps.
Well I have 4 computers all under 3 years old- they all do what my new one does- low 3-4's.

I think that test bed is a con. Am I right or off base. I was not allow to surf with it. They just go to Their speedtest site and bring up the results. At this point I think I got the once over................?

Any thoughts? Thxs All