Vista Premium to 7 Ultimate...

As long as you are going from 32bit to 32bit, or 64bit to 64bit, all you need to do is insert the upgrade dvd in the Vista OS and run the setup.
You can not change from 32bit to 64bit with an inplace upgrade. A clean install would be required, ie: boot with the W7 dvd and start instalation
Please NOTE all data on the Vista partition will be lost in this case, so be sure to backup what you don't want to loose.
I suggest you compare the difference between Premium and Ultimate on the Microsoft page before paying out a lot of extra $$$ for things you may never need other than bragging rights.
A couple of the things that may be of use to you, may be available in the Professional version which costs less.
In case you are not aware the W7 Professional is more like the XP Professional, in that all things in the Home Premium are also available in the Professional version.
Unlike Vista, Media Center is included in W7 Professional.

I don't believe you can upgrade from vista home premium to 7 Ult. You'd have to upgrade to Vista Ult first, then 7 Ult.

Just upgrade to 7 Pro. There are no ultimate extras in Win 7 Ultimate extras worth the bump. the only things missing from pro are Bit Locker, Bit Locker to go and about 7 domain specific features.

It is my understanding that windows-7 of any variety will require a clean install. It is probably a good idea to do this anyway. To preserve your settings and files, I think there is a migration procedure. Application programs will probably need a reinstall.

It is not clear to me how microsoft will detect/enforce the presence of a previous windows when using the upgrade sku(which is cheaper than retail)
XP required insertion of a previous cd, vista looked for a running os. A running os is not feasible if a clean install is required, or if going from a 32 bit os to a 64 bit os.

To assess your readiness for w7, download and run the windows-7 upgrade advisor:
http://www.microsoft.com/downloads [...] laylang=en

After more research, I find that the european versions will still require a clean install, not so for the US versions. That is because the eoropean versions can not be delivered with the IE8 browser
I think all of the ultimate code is installed with the basic install. Updating the product code is what activates the ultimate functions. Still, I think a clean install is the best way to go.
I base this thought on the current capability to upgrade vista in place via the purchase of an ugraded product code.

Vista Premuim BS to WIndows 7 Ultimate BS. That's not a bad upgrade if you ask me...