Crucial are fantastic.
I've RMA'd faulty memory with them in the past - the whole process was totally seamless.
Recently RMA'd my 256GB M225 SSD that I thought might be faulty (wasn't even 100% confirmed, it was picked up in BIOS and worked in Windows ok but I noticed some "volsnap" and "atapi" errors that - truth be told - went away after a chkdsk). Got a RealSSD C300 256GB SSD back as replacement, 2 days after they had received it.
Excellent service.