I have the Shark Navigator for about 3 years now. I LOVE it. Its lightweight, so I can carry it up and down the steps. Has a long cord for doing the stairs (I have 7 up and 7 down from the main level).
I do home daycare (so a lot of people thru my house daily, along with kids trudging some dirt and wood chips when they come in and out a few times a day), plus I have 2 long hair cats who shed like mad. I quickie vacuum every single day M-F, then usually a more thorough job on Sunday to prepare for my work week.
I clean out the canister and filter probably 2 times a week, sometimes 3. There is a lot of cat hair in there! But it never stops sucking stuff up, but I do notice its better when its emptied.
I love this vacuum and highly recommend it for those of us not willing to shell out what a Dyson costs or do not buy into the hype of the brand phenomenon. My hubby is one of these "research and review to death" sorta guys and that's what he did for me.
I always considered myself very very hard on vacuums. I use it every day. I have pets (used to have a giant breed, long hair shaggy dog too..A Newfoundland...then I used my vacuum 2X a day to maintain the house with my daycare business). But I am only on my 3rd vacuum in 22 years. Maybe we just take really good care of them? They all have lasted about 10 years each and I have never had a Dyson or Hoover or a Kirby. I had 2 Dirt Devils, and now the Shark Navigator.
I love this vacuum! I highly recommend it.