After using my new 17.5 Zipper for 3 long days I'll give it a thumbs up. I was surprised that it sucked down to the carpet harder than both the my other 13 and 15 Zippers. I mostly used my 15 and I didn't notice a big difference in weight going to the 17. I didn't have a problem with uneven floors either and I used it for 3 ten hour days on multiple jobs. If I'm able to use a Zipper on a job I'll go to the bigger one.