Everyone's different, so you need to decide what you want out of a 'backup' camera to your DSLR. Some here have expressed that they consider compact pocket cams to be more suitable to backup a DSLR. I personally went the other direction - for years I shot with a DSLR and a slim pocket camera as a second body, and I found myself just wanting more of the DSLR experience and capability, but in something smaller and lighter. I finally broke down and bought a NEX-3 originally to serve as a 3rd camera system, slotting in between the DSLR and the pocket compact. It worked so beautifully as a second body for me, being capable of completely replacing the DSLR if need be while still delivering identical quality and capability, or riding along as a second body with the DSLR so I could swap cameras with different focal lengths, that I ended up getting the NEX-5N and a few more lenses, a few adapters and a bunch of old manual lenses, and the EVF attachment as I do admit I much prefer to take photos with a viewfinder rather than an LCD. Since getting the NEX-5N and EVF, I find that I split my shooting time much more equally between the DSLR and the NEX - the NEX actually ends up getting a bit over 1/2 the shooting time on vacations and world travel, where the smaller size and less conspicuous package help in seedier places, and the DSLR gets a bit over 1/2 the shooting time around home mostly due to my bird and wildlife shooting where the DSLR still maintains some advantages. Though I often bring the NEX with 55-210mm lens to act as a backup body when out birding, because quality-wise it can match the DSLR and is so light and small. When the hot hot summer comes on, I end up going to the NEX body for 75% of my birding, because spending 4 hours walking 10 miles through the swamps in 100 degree temps and 90% humidity is just that much easier with 1/2 the weight!
The one thing I have learned is that the NEX system is actually the perfect backup to a DSLR for me. My pocketable compact, which was still to serve the duty as the 'portable' have with me anytime camera? Hasn't been used since I bought the NEX. I discovered that 'pocketable' simply wasn't an important feature for me...smaller size and weight were very important - and the NEX system is always lighter and smaller with any equivalent focal length lens to any DSLR kit. I can strip off the EVF attachment, and attach a 16mm pancake lens to the NEX, and it will easily slide into a coat pocket to go to dinner, or sit in my car's cupholder when driving around...so the NEX can substitute well for me for those have-anywhere camera moments for me. Even with a slimline compact camera that was small enough to slide into a tight jeans pocket, I still never actually 'pocketed' a camera - I usually hung it around my neck. I just don't like putting cameras in pockets. So the NEX hanging around a neck, or slid into a jacket pocket, is light enough and small enough to suffice for me...and has better image quality and flexibility overall for me compared to a compact camera, since it can shoot at huge ISO, can change lenses to meet any conditions or adjust focal range, and has a nice big sensor for major cropability.
You just need to decide if what you were really looking for was a DSLR backup with near-equal capabilities and about 1/2 the weight and overall volume...or if you wanted a DSLR backup that could be pocketable and super-small above all other considerations. There's nothing wrong with either approach - it just comes down to what you need and what you consider suitable for that.
