Hi Scotty,
just some quick additional comments. Unfortunately, scenery in FS is quite complex, therefore it can be a bit confusing.
If you just want great scenery and fly, get the combo from geographx. This has everything you need to get flying, apart from airports. To add airports you can get some free ones and the RealNZ ones.
Mountains of NZ transforms the mountains in NZ, and only the mountains. The 75 m mesh is good, but the 20 m one is a lot better. If you're planning to fly a lot in the mountainous areas and VFR, there really is no way past the 20m mesh. For example, chasing Fox Glacer in a chopper with the 20 m mesh will blow you away - the 75 m mesh simply can't keep up. The performance comment is rubbish (sorry Albatross) the 20 m mesh has barely any impact. In fact the whole combo scenery is barely any impact on framerates on a 2Ghz, 1Mb system (the system specs on the website are very realistic). I don't think one customer regrets buying the 20m mesh, at least I haven't heard any complaints so far.
It is true that FSX uses the same topo data, but leave it the MS to screw a few things up. Milford Sound is completely ruined and across the counry you get rivers sitting on fake plateaus or digging into the landscape. With the FSX patch, the topo fixes this issues. BTW, if you only have the mesh, you still have the very poor default coasts and rivers. The topo fixes all of this and adds the complete road network of NZ to your sim. That's why you really need the combo (which includes Mountains, Roads & Rivers, and the landclass).
I know, I sound a bit like I'm just trying to sell my scenery, but to be honest, all I care about is that every simmer who wants great scenery gets exactly that. The combo pack from geographics delivers you just that.
http://www.geographx.co.nz/gaming.htmlLet me know if that answers your questions.
Best Christian