I'm looking to purchase an external hard drive, primarily to use as a backup drive. The one I currently have, "My Book" from Western Digital, died recently. I didn't even realize when it happened, but just saw that Norton reported that I didn't have a recent backup, which I thought was odd, since I have it run automatically. I don't know how long external drives are supposed to last, but this one was (I think...) about 2 years old or so. Before I go and buy another, I figured I'd ask around first for recommendations. In any case, USB 3.0 and 2 TB storage would be best for me, though I'd settle for USB 2.0 if there's a good enough reason to do so (reliability). I thought about getting a network drive instead, since my mom has 3(! don't even ask) computers, but all she uses them for is solitaire, shopping, printing coupons, and web browsing.
I bought http://www.newegg.ca/Product/Product.aspx?Item=N82E16822178116 a couple weeks ago. Had no issues with it and it's really fast. 2TB, USB3 Only thing is it does not have any automatic backup software, so if it's important to you pick up something else - but you could just download some other software anyway.
Typically harddrives are one of those things that last as long as they last. I've had some last only 6 months and others last a looong time (10ish years and counting). I can't recomend much as it usualy come down to budget and importance of the data being stored. For stuff that needs to last you realy cant go past an optical medium (DVD/Blueray) as they dont have the failure issue (outside a ROM failing but you can use another drive to access the data, or physical damage to the disk), though conversly that also has limitations of storage space. I wouldn't worry too much as to brands seagate/WD/Hitachi are all reasonable for the price (for a 'typical' user), while typically around the same quality with histories of good firmware with the occasional dud too. As to the backup software, some are good that come with drives but as usual you can likely find some better third party stuff around too, or even get some off the manufacturers software anyway. I typically back up manually myself as my data doesn't need backing up all that often and I use dropbox or an SVN server for the essential bits.
Nothing that I'm backing up is critical, per se, but some of it is important enough to me at least that I don't want to lose it (I'm not running a business or anything like that). What I like about hard drives is that they are fast, and I don't have to really think about it, except when setting up and scheduling them. I may also burn a DVD or two if I feel I want/need redundancy for anything really important (at least that was my idea when I decided to get a burner instead of a simple player), but I really have never bothered to do so. I think I've burnt maybe 2 or 3 CDs in my whole life (I probably should do that more, but I'm lazy lol). And the hard drive has served me well recently, getting my data to my new PC (up until it died). If you don't think it makes a huge difference, I'll probably just get another WD drive then. 2 TB is simply overkill, but I can keep several different backups on it then and not worry about it too much. And it worked well enough while it lasted. That said, that's the shortest time I've had a hard drive last (with the lone exception of a drive that was DOA that I had purchased from a vendor (in hindsight, maybe a less than reputable vendor) at a computer fair.
For general advice, check this thread. http://community.gaslampgames.com/threads/mass-storage-devices.3416/ But be aware that prices change constantly and hard drives are finally getting cheap enough to buy. (The excuse of flooding driving costs to several times the original price is finally wearing thin enough to effect the price.) I think eSATA is a better option than USB3 or anything else. USB3 may work fine, but if any device is going to fail, if it is USB based, the odds double or more. eSATA is exactly the same as SATA and has the same speeds as USB3 for mechanical hard drives since none of them can beat SATA 2 speeds. (Most mechanical hard drives cannot beat SATA 1 speeds.)
The last external hard drive I had (made by Seagate, IIRC) died while I was backing up my main, regular hard drive. At this point I'd have to recommend either a DVD burner or a small pile of 8+ GB flash drives.