Another good service to check out is Tresorit. I used Sync.com for a few years but switched over to Tresorit because it was cheaper (at the time at least), more

Another good service to check out is Tresorit. I used Sync.com for a few years but switched over to Tresorit because it was cheaper (at the time at least), more stable for me, and has significantly nicer clients (and supports Linux + has great web access). The premium plan will get you less storage than Sync.com (at the current sale price, ~$10 month gets you 500GB vs. 3TB) but if you don't store huge amounts of stuff on cloud services, I'd highly recommend checking it out too.