What performance issues/symptoms can a pilot expect while taking off above MTOW? Lately I've been flying a Cessna 162 Skycatcher, primary as a cheap way to build time towards the Instrument Cross Country requirement and my glider club's hours requirement to tow gliders.

One issue with the 162 is it's relatively low Useful Load.  Here are some figures relevant to my question:


Maximum Takeoff Weight: 1324
Equipped Empty Weight: 857
Useful Load: 467
Weight of full fuel: 24*6 = 144 
Weight of 3/4 fuel: 18*6 = 108 
My Weight: 215
Max Weight of passenger full fuel: 108.24
Max Weight of passenger 3/4 fuel: 144.24


Note: All Weights above are in pounds(lbs).

Because weight is an issue with this plane and almost any passenger I would consider bringing along, there is a diagram in the FBO's flight book that can be shown to the person fueling that depicts points inside the tanks that denote full, 3/4, 1/2, etc:



Last week, I did a flight with a 130 pound passenger.  On the first refueling I was sure to show this diagram to the person filling to ensure he only filled to 3/4.  I generally make it a habit to inspect the tanks after fueling to ensure they have not gone over the asked for amount.  Takeoff was normal with no noticeable degradation in performance.  Note: the fuel gauges in the 162 tend to show the same value whether the tanks are full or 3/4 full, with no noticeable decrease until until values go below 3/4.

We then proceeded to fly roughly 1.5 hours to another airport.  At that airport, I went through the same routine but (in a hurry of course, isn't that how most mistakes are made!) I did not follow up to ensure he had not "overfilled" the tanks.  On takeoff, I noted a notable (though by no means catastrophic) degradation in performance:  


I needed more runway to rotate.
I could not climb above 55kts (Vx/Vy in the 162 are 57/62).  


As I was able to climb at a safe enough airspeed, things seemed to stabilize and I had no other issues, I chose to proceed with the return flight.  Performance for the rest of the flight was fine with no extra RPM needed to cruise or do later climbs.

It wasn't until I was thinking about it later that it occurred to me that the refueler might have filled my tanks to full.

So my question is, do these symptoms sound indicative of being overweight?  Or, more generally, 
What performance issues can a pilot expect while taking off above MTOW?

Note: I have reviewed several questions related to this, including:


Can a commercial airliner be too heavy to take off?
Does weight and balance of an airplane matter more on takeoff?
Questions tagged with weight-and-balance


However, I didn't find a question dealing specifically with the performance degradation felt by a pilot taking off above MTOW.

Update

After thinking on this a bit more, reading some of the answers and talking it over with my daughter (the passenger mentioned and a pilot in her own right), I'm leaning towards a different conclusion.  Since I was first checked out in the 162 last winter, this was the first time I'd had a passenger.  My first takeoff was from KJYO (5500 feet runway length / 390 ft elevation), whereas my second was from Eagles Nest (W13) (2004 ft runway length / 1436 ft elevation).  My new theory is that what I felt on the second takeoff was the added weight I wasn't used to since I've flown the previous 20+ flights alone.  I believe I didn't notice this as much on my first takeoff because I had much more runway to work with.  

Nonetheless, I think the question and answers are still relevant/useful.
Firstly, you did goof up by not checking what the refueler did. Your life depends on that fuel, and in light aircraft the gauges are notoriously unreliable. We've probably all done it but we shouldn't - always check!

However going off your figures you might have been what, 20 pounds overweight? That shouldn't cause such a massive decrease in performance. MTOW isn't an on/off switch. It's a point that has been selected as the maximum allowable limit - with a safety margin built in. You should never exceed MTOW even by a bit, but if you do you will (hopefully) live to see your kids birthday thanks to that margin.  

I've flown a C172 right at MTOW (actually about 5kg under but close enough). Acceleration is slow, meaning you use more runway. Rotation actually feels normal thanks to ground effect, but once you leave that you notice a degraded climb performance. If you're over MTOW these effects are the same but amplified. If you are very overweight, you will climb in ground effect but will struggle to go much higher than 20-30ft. 

As for your flight though, it could have been affected by a tailwind or high temperature/low atmospheric pressure. What was the temperature like on the second leg? Vy will theoretically get you the best climb rate even above MTOW so it doesn't make sense that you could climb below but not at that speed. Maybe there was something localised affecting the ASI, or, if I may be so bold, your technique on the day wasn't 100% :)