I did the same, but with a 5000W unit. That was all I could find a couple days before Sandy. After Sandy I had the transfer switch put in. I'm able to run garage doors, 2 fridge/freezers, a bunch of lights, hot water heater (gas, but has a fan), internet, gas furnace (start-up), sump pump. That's really all I need. Not all of those things are running at the same time, and we try to conserve during a black out. I have thought about upgrading to 7500W (maximum for my transfer switch) but there's always something I'd rather spend money on.
Since Sandy, I've used it 5 or 6 times. A couple times for short (less than 3 hour) outages. A couple times longer (once for 36 hours). The whole set-up with the generator, switch, labor, was under $1,500. I'm slightly jealous of my neighbor's whole house set-up, but I think the bang for the buck was good enough based on our limited outages.
The negatives are obvious: i) doesn't turn out automatically so I have to go into the elements and if we aren't home we could lose food; ii) they say you aren't supposed to run the portables in wet weather, but the majority of the time we lose power is during wet weather; iii) if we have a substantial outage during the summer, it could get hot in the house (I have a portable ac unit that I haven't tried yet); iv) it's pretty loud; v) I keep some gasoline around, which I get rid of every couple years if I haven't used it.
The positives are also pretty obvious: i) it was $10k cheaper than whole house; ii) it runs on gasoline which I was able to get easily, even during Sandy; iii) it's portable so I've been able to lend it to friends who had outages that I avoided.
