Hi dubtastic,
It all depend on what you want. If you want to be more green and use less power, then I would get a Macmini Server quad-core. I would wait til they released the next gen Macmini 2012 which I am waiting on replacing.
Since you mentioned that you want things to be able to sync more easier and managed for different "iDevices" I would recommend Mac OS 10.8.2 with OS X Server 2.1.1.
I know it's has been a pain for sometime transiting from 10.6.8 Server to 10.7.X and to the earlier versions of 10.8.1. and OS X server 2.1.1
I know SMBX has been more stable for my clients on 10.8.2 Server with OS X 2.1.1 app. Then compared to Lion Server 10.7.4. However, most of my clients that are using SMBX are using Office 2010 files and pdfs.
I know recently transitioned my clients Lion Server 10.7.4 to 10.8.2 when they released OS X 2.1.1 app. And only used my own business macmini as a test bed for 10.8.X server..
Some of my clients offices are about 30+ Mixed with WIndows XP Pro SP3, Vista, and Windows 7 and a Windows 2008 R2 Terminal Server that's an 2x 4core Xeon Processor.
Then some of them have 30+ ipads in the field for patient intake info. Too bad Apple is not supporting iOS6 for the original iPad which I'm a little upset since the iPhone 3GS is supported.
Basicaly my clients use OS X Server as file, mail, web, and iDevice server.
It's true that 10.8 Server has less GUI controls, well then start diving into command line controls and configuration files for more advanced options. It's not bad once you get use to it.
over all now it's pretty stable with 10.8.2 and OS X 2.1.1 app. I know I can't comment on the Indesign file issues that I read some ppl encountering since non of my clients use indesign so far.
As for deciding for a computer, it all depends on the companies needs and how many computers they will be serving and how large of storage space they'll need and is energy consumption a concern.
I know most of my clients aren't that big since they have under 100 employees and a quad-core macmini is fine.
For me personally, I do have a Mac Pro 2.8ghz Dual quad-core Xeon Processor Early 2008. I don't use it as much anymore besides editing Wedding Photos and other kinds of Photos and I love the storage space. However, I would not want to leave it on full time since it consumes a lot of power.
Therefore, I have a late Macmini 2009 Server which is left on full time for web,mail, and file sevices. For FTPS I use pureftpd manager 1.8 combined with a recomplied version of pureftpd 1.0.36
I still haven't dealt with my personal storage issues since I am a part time wedding photographer I do need a lot of space which so far My Mac Pro with mirrored drives solves that issue partially.
I plan on getting the new version of the macmini server and will probably end up getting the new Drobo 5D storage device when that gets released.