@Pfk We have a clamshell iKamper copy (from a company now out of business) and it's cavernous. We love the room it provides for both of us and our two 60-70 pound dogs. With that said, iKamper 100%. Don't even consider a RoofNest if the iKamper fits the budget. The outward appearances may be very similar, but the attention to detail and quality differences are readily apparent. This is only compounded by everyone else still charging iKamper-like prices.
When it's time to replace ours (unfortunately probably sooner than later), the only thing that may keep us from buying iKamper is that they don't offer an aluminum shell like a couple others. That's a very attractive option here where there are many low-hanging branches that can do a number on an ABS or polycarbonate shell.