I forgot something that I should have put here, when talking about the new coins to be released this year (we could start seeing them within a couple of months by my reckoning). The 50p coin is the most radically changed design. It will retain its seven-sided shape, but instead of having a base at the bottom so you can stand it up and see the design the right way up, it will be upside down. And the obverse ("heads") will also flip at the same time. So we'll have one of the points of the heptagon at the bottom rather than the top.
Which current design is your favourite though? Let me know on the poll on the left... it closes in only 4 days!