Once the 90-day trial ends, users who want to continue using the OS will have to purchase a copy and perform a clean install, including drivers and applications. And, the trial is really intended for IT Pros who, for some reason, don't already have access to the new OS.
Microsoft says testers can continue to use the trial after program ends, but warned that the OS will shutdown once-an-hour after the expiration date. How's that for nagware?
Also, Win7 Enterprise will not be sold at retail, so the release version will be fairly easy for corporate customers to acquire, but more difficult for smaller businesses and individuals. Of course, they also won't need many of the enterprise features.
The number of trial downloads--available here--will be limited, Microsoft said.
Potential trial users, should also be aware that members of the following MS programs already have access to the new OS: Partner Program, MSDN Subscribers (developers). TechNet Plus subcribers, and Volume License/Software Assurance customers. If you work for a large company, ask around before downloading.
"We do not recommend that you install this if you are a not an IT Professional or not professionally managing corporate networks," Microsoft warned.
The hardware requirements and other limitations are described on the download page.
My advice: Don't download the trial to any machine you are planning to use in production and don't be upset when you end up having to wipe the hard drive at the end of the trial.
If you can live with those limitations, the trial may provide a way for almost anyone to get some Win7 experience ahead of the Oct. 22 release. Just don’t tell Microsoft that we sent you, OK?
(If you haven't seen it, here our Win7 upgrade FAQ).