Compared to an iPad 1, it is a huge improvement so is almost a no-brainer purchase. The only reason to wait would be for what many people expect in the next version which is a retina display (that is why I am waiting). Then again, the iPad mini has the same resolution as your iPad 1 but with a smaller screen so if you don't mind the iPad 1 resolution you will be happy with the iPad Mini. There are actually some performance issues with the retina iPad (third generation) so hopefully they can overcome them when the iPad mini gets retina.
I guess another consideration is whether you wish the iPad was smaller/lighter and easier to take with you since that is where the iPad Mini really excels compared to the full size iPad. You also get the new IOS 6 features including Siri that you can't get with the original iPad since it can't be upgraded to IOS 6.
I agree with @bb4u ...iPad Mini is more portable so if you are a traveller you should get one ...
Well my advice is ... if you are not in hurry wait for iPad Mini 2 (because of retina display)