I can echo others comments about Windchill support calls versus Creo. I would definitely recommend maintenance on going. If you have the Creo license level that comes bundled with Windchill as you said, you may want to consider only having as many Windchill users as you have Creo users. If you need extra non-Creo users in Windchill, you'll have to buy more Windchill only licenses. Note they come in different usage levels: Heavy, Light, View and Print. Though I have also seen the descriptors Author, Consumer, and View and Print. There are predefined ratios required of Heavy to Light. (Author to Consumer)
Another option is to consider PTC's cloud offering? It seems really cost competitive, especially when you factor in the cost of paying:
We are planning on moving to PTC Cloud at some point. It is very cost competitive to the build your own solution on Amazon. I did an intensive investigation on the subject and talked with the admin of a company that uses PTC Cloud with great success.
I wouldn't want to tackle Windchill installation, configuration, or management without access to both PTC's knowledge base and tech support. Creo and Windchill are way too buggy to not have access to the latest maintenance releases, service packs, and patches. Technically, having maintenance on any product would get you knowledge base access to all of them, but if your Creo seats are already bundled with Windchill then you will have full support for Windchill anyway.
I just took a quick look and since March of 2011 I've opened 235 tech support cases. (Sometimes I feel like a beta tester for PTC.)
Pro/Engineer & Creo
By the way, if it's not obvious from the numbers above, we went from 9.1 + Wildfire 5 directly to 10.2 + Creo 3 (all by ourselves!)
At my previous employer I was able to install and configure Intralink for CAD data management. Once configured, you could pretty much forget about it. With Intralink I could be the system administrator and still be a productive CAD designer. Now that I install, configure, and maintain Windchill and Creo, plus install and maintain all the server related equipment and virtual machines (for production and development environments), I have zero time for actual CAD work. (I'm okay with that.)
While I'm a huge fan of using technology to stop the "shouting over the wall" about who has what file open, Windchill is not a low cost proposition. You're either going to dedicate a person wholly to it, pay a VAR to do it for you, or pay PTC to handle it (via the Cloud). Either way, you are going to spend a lot of money. If you have a really good internet connection, the hosted solution might not be bad, but fundamentally you are re-buying the software again. Your existing licenses won't count at all towards your cloud licensing expenses.
We were, up until our recent migration, a PTC Cloud Services customer. They do a great job, especially since purchasing NetIDEAS a few years ago. We moved away from that service only because we were wanting to do things that couldn't be done cost effectively as a service.
For the company with the right set of requirements, they are a great solution. Just a couple of things that you might want to keep in mind.