I have never made a Mr.Beer kit, but have tasted a couple. Not my "pint of beer" but it works for getting people into the hobby. I will say there are a few things I have learned while brewing and judging. If anyone decides to brew their own beer these are the things i would encourage for best results.
2- No matter the sized of your batch, do full boils of your wort. Yes, there is a difference between partial and full boils.
3- Oxygenate your wort after boiling. Yeast needs oxygen!
4- If you are using tap water, use a carbon filter
5- If you brew once or twice and like it, invest in an Wort Chiller. It can be an immersion or counter-flow. Buy one or build it yourself. This is a must have.
5a- Make yeast starters if you decide to make this your hobby
6- RDWHAHB (Relax Don't Worry Have A Home Brew)
7- Before going All Grain do some soul searching. It requires significantly more time and investment. It is one of the reasons I haven't brewed in 4-5 years. I'm thinking of going back to extract kits for ease.
8- Invest in this book http://www.howtobrew.com/
and you can read a few chapters here http://www.howtobrew.com/intro.html