I upgraded my Inspiron 1721 a while back to Windows 7 x64 without any issues. I did a quick peek on the specs of a 1525 and the look about the same as mine.
I decided to use all of the "built in" drivers that Windows 7 would detect and install and had no problems at all. I'd say let Windows 7 stay as "raw" as possible with the drivers they provide, and only pull the Dell ones if you're having some odd performance issues or the hardware isn't detected.
In a few cases where I needed to pull drivers off the Resource CD, the x64 version of them worked fine. I think the only device I didn't "recover" was the special touch pad driver, so I could use it, but didn't have access to the horizontal and vertical "scroll bars" on the edges of the touchpad.
That said, I was quite happy with the upgrade, and had even better performance out of it than when I was running Vista on it. I had 2GB of RAM, and I'd recommend keeping that level or higher if you're going to do the upgrade.