Hi Shell,
What features you’ll miss sorta kinda depends on what features are important to you. You will get way more useful feedback if you provide some info on how you currently use Scrivener, so we can tell you how that will change.
For me, I love using iOS Scrivener on my iPad Air 2. I’m on it daily and am a big-time fan boy. I too am working on a novel, and probably 100k of the book was written using iOS Scriv. It is awesome (iOS Scriv, not my novel 
).
That said, I could never use it exclusively, due to iOS Scriv’s compile feature, or lack thereof. IMHO all Compile is good for on iOS Scriv is proofing rough drafts. If you use Desktop Scriv’s compile for pretty much anything else, you’ll need to keep Desktop Scriv around in some capacity. Launch a project on your iPhone and try to compile it, and you’ll quickly see what I mean.
The other main things I miss on iOS Scriv are Snapshots and Keywords - neither of these are supported.
Finally, iOS Scriv can do zipped backups, but it’s a completely manual process.
What that means for me in practice is I use iOS Scriv for the actual drafting and rewriting, and Desktop Scriv for project level structural stuff and prep/housekeeping work (e.g. making snapshots before revising documents). I also write in Desktop Scriv when I’m on my treadmill, because my laptop balances better than my iPad does on the treadmill’s console section, but you probably don’t care about that.
Best,
Jim