I can not comment on the Dell Zino HD because I have never used it. I do have a (late) 2009 Mac Mini as an HTPC with the HDHomerun setup.
The mini does have build in blue tooth, so you should be able to use a BT device to control it, and no have to worry about line of site. I use the Logitech DiNovo Mini. I have also use the android remote app for XBMC too. As long as your signal is good, I don't see an issue. Otherwise, you'll need to get some kind IR repeater blaster.
The HDHomerun is an experience. I have it, currently use it, and like it. It is very obvious Silicondust prefers Windows. If you have Windows 7, it's a really nice experience. MC7 works great, and easy to setup. Has PVR functions that are intuitive, and a EPG at no extra cost. If not, you can download for Silicondust some software called QuickTV that lets you watch live TV. It has no PVR functions. But you can set it up to watch separate incidents--limited by how many tuners you have available. It also can play some analog channels (or digital broadcast set to the analog channel). They're are other Windows programs you can use such as SageTV, GBPVR, MythTV. If you have WindowsXP, HDHomerun is not a great experience if you want PVR or EPG. There are other limits with XP in the whole HTPC.
In OSX, the biggest issue is the amount of software available that can use it. I used OSX for a short bit on my HTPC. The defacto software is EyeTV. From what I read it suppose to be really good. Suppose to have PiP. I never tried it because there is no trial program or period, and it's $80. I wasn't willing to pay that much for something I only use once a week to see TV and about once a month for PVR. I tried out SageTV; has a 30 day trial period. It worked pretty well. I had some quirks with it, but I think it was more my setup than the software. The experience of using it, just did not appeal to me. It's input controls did not work well with DiNovo Mini. I could not get MythTV to install correctly; I wasn't familiar enough OSX. There is the The Tube as well, but it couldn't see the HDHR. Also, Silicondust does not include any kind of TV viewing software like QuickTV. Plex does have a plugin/addon that can let you watch TV. It's really early in development, but it works. There is no channel surfing or EPG. It sets up like TV or Movie sections where each channel is set as content. Maybe in the future the addon will function more like a TV. On a side note, QuickTV is the same way, but it has the TV stations to the side, so you can click to change channels quickly versus having to to the menu.
I do not think the mini runs hot. It has no fans, so its super quite. The only time it makes any noise is accessing some of the hard drive or DVD rom. I felt it a few times after using a while, and it just felt warm. I have mine in my entertainment cabinet.
In fact, I have a thread on another forum (a game site with some home theater enthusiasts) detailing my experience on setting up and use the Mac Mini as an HTPC Mac Mini Tinker Toy
), you may want to check it out. If you read it, realize I've been a Windows user since the Dos 4 with Windows 3.1. I've had only use apple machines here and there.