Well, Windows 7 (at least the Beta) is nice enough. It has some nice windows management features, lets you fine tune ClearType, faster performance, etc. The most significant changes are likely to be its reduced memory usage and some fairly subtle changes like the new Library metaphor for file management.
Bear with me a minute. Like Vista, 7 uses memory very aggressively to cache files and code, so on a system with a reasonable 2-3 GB of RAM, memory usage isn't much lower than Vista. But, it runs much better than Vista on systems with limited memory, so it represents an effort by Microsoft to be more competitive in the netbook/cheapskate PC market.
The Library lets users group any folders they want to use for data storage into an easily viewed and managed location regardless of actual location. Why this matters is that we are going to be seeing SSDs offered as high end options on computers sold to fairly unsophisticated users real soon now. Almost certainly, these will be fairly small drives running the OS and software, while most of the data storage is done on a hard drive. For the typical user, I think the Library will make file management easier on a multi-drive system. Overall, I think it's fair to say that many of the changes from Vista to 7 are targeted at new users and first time computer buyers. For those of you who've been around a while you might remember that the XP interface was designed with the same goal in mind. And you might even remember how much long-time Windows users bitched about it.