I've been interested in trying the W10 Technical Preview on my 3yr old Vostro 3750 laptop but find that currently it seems unable to run (or fully install) the new OS. Currently it runs W8.1 which I clean installed and this runs like a dream.
A couple of months ago tried an upgrade install of W10 to get a feel for the process and the new OS. The upgrade took 7 hours (despite my 8.1 install being a compact 24gb) and I was left with an unusable PC with the CPU at 100% despite several reboots and trying to investigate exactly what processes were causing this. So a failure... roll back to 8.1 with Acronis.
Yesterday I tried a clean install of W10 using the latest build and on a freshly formatted partition. The install was quick at just 15 minutes or so but then inexplicably froze at the point at which you enter your MS account details in the initial set up. A search of the popular '10 forums' site showed a new thread with others experiencing the same. One was also a Dell. So again, roll back time with Acronis.
This seems quite a serious issue because were this to happen when W10 goes live on July 29th, then there are going to be lots of 'user unrecoverable' systems out there.
I don't know where the problems lie... W10, or some problem with the Dell setup... but currently W10 is a no go for me.