When using a 60 watt power supply from the old laptop with the new one, it still worked but every time I plugged it in it said that 90 watt would be ideal but not necessary. So as long as the plugs the same, they should work. Hell, I even used HP power supplies on the dell and it worked no problems
I'm glad it's worked out well for you. Just keep in mind that it's not always safe to use a different ac adapter, particularly if the voltage is wrong. Some devices have a wide enough voltage range that a slightly different voltage range is acceptable, but not necessarily will any adapter that physically fits work. In terms of current, you need a current rating high enough to provide the necessary energy to run the machine. For safety, you should always use a current rating high enough to provide the necessary power (watts, W = V * A). Because the voltage needs to be the same, this means you need a current equal to or greater than the original current on the ac adapter.
A message saying a higher watt power supply is recommended would be related to the fact that ac adapters are rated with maximum output specifications. An adapter rated for 90w (example 4.74A) can supply 60w (ex. 3.16A) without trouble, but if the system attached to it requires 80w for a period of time (it's being stressed for some reason), a 60w supply can't safely meet that demand.
It's great that you haven't had any issues, but the physical fit is one of the last things you should be worried about. I or another user may have an adapter that works for roaming pear, but I personally wouldn't feel comfortable sending one unless I knew I was sending something that wasn't liable to fry something or start a fire.
