Bought it - Hated it - Sold it

For those who made a mistake in buying a particular M.H. 

a. What did you buy? 
b. What about it you disliked so?
c. How quickly did you get rid of it? 
d. How much of a beating did you take, or rather, how expensive was that lessen learned? 
e. How and what would/did you do different in your next purchase?
f. What was your next purchase and did you get it right this time?

I suppose I will go first, although I consider these things as somewhat minor annoyances more than anything else.

bought a used Winnebago Lesharo (best mpg 22, fun and ease to drive, can go anywhere)
will never buy again with bed you can't walk around to make easily or a tiny fridge that can't hold much
it was very good for what it was made for, so I didn't have to take a loss on it after traveling the NW over 2 months
it may be cute and fun thinking small, but learned that size matters a lot more than you first think
it's just too limiting to live full-time in something much under 30'

Due diligence has helped my avoid most of those decisions.  I like to go in and test everything Electric, Water, Propane to make sure it all works and then if I/we like it go for a test drive.
Regardless of what we pick out there will always be stuff we want to change.
Marvin

Im guessing most of these answers are going to be bought too small. You might get the odd one who bought a 45 footer and found it too big for lots of places. Otherwise, as everyone says, floorplan, floorplan, floorplan.

2002 Prowler 25 ez
Disliked the small size BUT was still excited to own it.
Traded in 9 months later
didn't lose anything.
Better inspect for water damage.
2006 Denali big honking fifth wheel and yes, I think we got it right!

Ok, I'll be the first to state I did the "What the heck was I thinking" walk of shame. We started our RV life with a brand new pop-up, no problems what-so-ever with that, until it became a nightmare when we had triplets and realized how difficult it was to set-up and break-down while trying to wrangle three toddlers.

So we moved onto to what we thought was a good idea, a class C MH. To start off with, we didn't have the finances at the time and thought we could pay cash and get something decent. We spent $10k on a 15 year old MH. The person had "fixed" a hole in the roof with what I though was appropriate materials, but were not actually RV appropriate materials. Guess what, it leaked. And had been leaking for some time. Doh! Strike one. Got that fixed, thought we were ok.

Next, while on the maiden voyage along the West Coast during early September, an unexpected rain shower occurred. Guess what? We could take a shower under the AC! The seal had failed... Strike two.

On the return home from that first trip, we kept having to reset the refrigerator to keep it cool when on the road. When hooked up we had no problems. We stopped and got some deliciously fantastic cinnamon rolls with loads of cream cheese frosting. Yum! Then we hit a heat wave part of the way home and didn't realize how warm the refer got. Yep, you guessed it! Food poisoning! Fortunately, we were  home by the time the full effects kicked in. Turned out the circuit board that controlled the propane valve had been recalled and never replaced. STRIKE THREE!

Got it home, got EVERYTHING fixed and repaired and sold it for what we bought it for. We figure the cost to repair everything was probably about the same that we would have paid for flight, hotel, and car rental for the two week trip. So at least we could tell ourselves that we broke even. Chalk it up to one BIG learning experience. We have since moved on to bigger and much better things.