Put the original RAM back in. Boot the system and hold down either the Command+R key combo or the Option key. Command+R will take you directly to the Recovery partition. Option key will give you a screen where you can select which bootable drive/partition to boot to, select the Recovery partition.
Once you are in the Lion Recovery select Disk Utility. In Disk Utility Partition the Macintosh HD as 1 partition using Mac OS Extended (Journaled) as the format and click Apply. When that is done exit out of Disk Utility and select Reinstall OS X Lion. click Continue and wait. All your files will be gone and the OS will be downloaded and reinstalled. Once that finishes use the power button to shut the system down. Then take it back to the store and get either your money back or new unit. Or get your money back and buy a PC.
I am also a LONG TIME Windows user, along with Linux, and have had 3 Macbook Pro's this year. I usually take them back in the first 2 weeks but the one I have now I'm keeping.
Mac is a computer. IMHO no better or worse then a Win PC, just a little different in some ways. But they are both just computers and basically work the same. Some things I like and some thing I can't stand.
Good luck at the store. You shouldn't have any problems.
When you wrote that the trackpad "wasn't as responsive as expected," did you mean that the screen pointer didn't move as quickly or as far for the same Trackpad swipe as before?
If so, you can change the trackpad's responsiveness - regardless of whether you're using "natural" or (umm) unnatural scrolling - by just changing the following setting on your Mac: go to
System Preferences > Trackpad settings > Point & Click
and go to the horizontal slider called "Tracking Speed."
If you set the Tracking Speed slider to "Slow" then sliding your finger across the Trackpad will result in the screen pointer moving very slowly across part of the screen. In contrast, with the Tracking Speed slider set to "Fast" the same movement on the Trackpad will make the screen's pointer fly across the screen in no time.
Adjusting the tracking speed also changes the horizontal and vertical scrolling speeds.
The only odd aspect to this, is that changing the scrolling direction shouldn't change the Tracking Speed, unless you accidentally brushed against the Tracking Speed slider while you were changing the scrolling direction.
(Note! I'm using a desktop Mac with an Apple bluetooth trackpad, so my suggestion may not be completely accurate.)
I can see where the confusion came from. What I actually meant was that it doesn't track as well. My MBP keyboard seems to require more consistent force to use it, as opposed to the Air, which seems to work better. I'm brand new to trackpads - don't really care for them, have always used the ThinkPad "nub" - but the keyboard on the Air was so responsive, it played a roll in convincing me to buy a Mac. I'm sad to say the MBP pad, or at least mine, doesn't seem to work as well.