I love upgrades and I usually spend my miles on upgrades and I told you that in our chat last night. However, I do not have tons of miles to use so I have to decide carefully when and where to use them. In the US the First class service on flights under 3.5 hours is generally lame and not worth it TO ME to upgrade unless I have a coupon because I have limited miles to use. I try to upgrade on transcon or international routes.

Also, First or Business class seats on narrow body planes tend to be small. I fly alot from NY to Florida on small MD80 aircraft. The First seats are tiny, there is no entertainment and breakfast service is cereal and milk. An advance coach ticket on this route costs about $98-198 depending on the routing and for the price suits my needs just fine. Therefore, if your pool of miles is limited and you decide to go First class, try to save your miles for longer flights especially on international routes on wide body jets where the service is everything you expect it to be. If you have almost unlimited miles then there is no reason not to go First all the time.