Yes, i did have a Thunder and a Lightning at one time, both of them are now sold and gone. I can't say that i miss them too much. They were the best for their time, no doubt. However, i have to say the Dyson is the best (In MY opinion) BAGLESS, and i stress the BAGLESS to save my ass from this forum because i know people get mad about that kind of talk.
I've owned a DC07, which is not the best whatsoever, but it had a lot of potential. Then after that i owned a DC17 which, at the time, i thought was the best bagless vacuum on the market. It was aggressive, simple, and i had never seen a bagless vacuum pull so much dirt from anyones carpet. However, this weekend i acquired a DC28 AirMuscle Machine and it is awesome! Yes, the AirMuscle i can already tell is going to be causing me some issues in the future, but, now that it is still new and i can enjoy it, i love it! It is aggressive as all get out, and it pulls itself on just about every surface. It is great!
Again, that was all just my opinion.
Hope this helped,
Kyle