I've yet to call Samsung about anything so I can't comment on theirs.
I had an issue with my 840 Pro when I could not activate the 'Over Provisioning' feature in the software suite. Every time I tried it kept displaying an error saying there was insufficient space. I thought "WTF?" "It's a 256 Gb drive with only 36 gigs used, how can there be insufficient space?"
Anyway, to cut a long story short, I contacted Samsung Support and the issue was resolve 3 minutes into the call. Turns out a firmware update borked and just needed reapplying.
As for Samsung 840 Series prices, my 256 gig Pro drive cost me AUD$209.00 [they can retail up to AUD$300 in some outlets] a 240 gig EVO cost me AUD$!89, and my 840 Series 120 gig standard SSD was just AUD$89.00, so they're very competitively priced as well as being of great quality.
I've just been to the online store I use these days and they have a 1TB Samsung 840 EVO Series Sata III for AUD$680. Given that many 500gb SSD's are around AUD$600ish, that is very interesting indeed. It's currently out of my price range due to the cost of my new Intel i7 4770K build [using a 512gb 840 Pro for that @ AUD$469.00], but a 1TB EVO is on my radar for a future upgrade, and by then they may be even cheaper again.
Oh, @ Crastiloowa... thanks for the links, they're gonna be quite useful.