You might want to try some polarizing filter?

For your last 2 picture of overexposed and underexposed, seems like you're facing the common problems. You can try using the polarizing filter or combine the 2 picture into HDR.

Yea, I'm talking about the CPL; You can try it and see the difference; But I think the kit-lens have rotating front elements which makes using CPL difficult.

Anyway, for the last 2 picture, which you have both overexpose and underexpose, HDR will give you the best result from both.

True, once you hold the bigger bodies, those dials, top lcd, etc.....

Why not? Depends what one is looking for. for me, D3100 is more suited for people who just want a DSLR, cheap and easy to use. For more serious into photography, you'll find the lack of controls, info display, etc.

Just my personal opinion 'lah'. Nothing wrong choosing either one, it all depends on personal preference and what one is looking for. As for price difference,it really isn't much difference, if you're considering stepping into photography/DSLR... If the small difference is a big matter, maybe one should forget about DSLR and go for semi pro point and shoot, easier to use and still deliver excellent results. Sometimes, people just want to get a DSLR, so its important to know whats the purpose and why they want it in the first place.

Utilize what you have. When you reach certain level and limitation, you will know what you want. Won't pening.

550D is also entry level like D3100, small basic body. D90 is different level.

Go for the Non-OS version, much cheaper, but it's 18mm instead of 17mm.

If OS is not a must, can consider the 18-50mm EX DC Macro HSM.