1) If you really know what you want just buy it. Too many times I am unwilling to throw down on an item because it is just not quite a good enough deal. But I never say after I buy 'I paid too much for this
2) And almost always with any purchase there are compromises that I overlook. Usually because I am blinded by some percieved benefit my new purchase will bring. In the end the overlooked comprimse outweighs the benefit and I am wallowing in a mire of unhappiness. So, if making a new purchase make out a pro/con sheet and think about it. Demo the unit to death. The more expensive the unit is (relatively speaking) the more you think/demo and consider the purchase.
If 1) and 2) seem inconsistent, well...fine. Those are my mistakes and I stand by them.
Chris