The term 'appreciable' doesn't mean something is good, just that it's significant enough to notice. The project suffered an appreciable delay due to unforeseen problems.
Pro Tip 2/3
Measurable Change
'Appreciable' often suggests that a change can be quantified or specifically measured. After the budget cuts, there was an appreciable decrease in the quality of services.
Pro Tip 3/3
Subtle Yet Significant
Sometimes 'appreciable' is used when the change isn't huge, but it's important and not negligible. There's an appreciable difference in taste between the two recipes.