No, the new one is running very well. I'm using my HTC one at the moment, but I mostly use my Lumia 920 for the majority of my time. It's been a while now, and there haven't been any issues at all, the new 920 is great.
Honestly, being under warranty, let them swap it out for you. The front dust becomes irritating, because you eventually can't Skype, take selfies, or anything else you may use the front camera for. The warranty process is easy and quick, and doesn't cost you a penny. There isn't a deductible or anything for a warranty issue.
Just keep receipts of your return labels/tracking and paperwork that your carrier will send you as part of the warranty claim. You will need to send your device back usually within 10 days; make sure you do this. Also, make sure you wipe your device, so none of your personal info is left to potentially prying eyes.
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