Excellent Rated 5 out of 5 stars

This add-on is one of the best in its category. I have switched from Update Scanner because SiteDelta has more facilities and is able to find updates to specific regions of the page.
Although the developer has tried to make this add-on as intuitive as possible I found it necessary sometimes to refer to the web site ‘features’ tab for help with specific functions .........
http://sitedelta.schierla.de/features.en.php
The Watch & Ignore Regions facility is excellent when, for instance, you require update notifications for a specific thread within a forum page.
I do not understand why this add-on is not more popular. I did not find it within search results when searching Updates & Alerts using search terms like 'updates' or 'alerts' or 'notifications' but found it from recommendations of others within the user reviews of other add-ons within that category. I guess this is down to the search words that the developer has chosen like 'change' & 'update' instead of 'updates' & 'notify'. SiteDelta is also an excellent name but does not immediately inform the user what the add-on is about.
If you like pop up notifications you may find the 4sec display too short. This can changed via the Firefox about:config setting in alerts.totalOpenTime but be aware this will affect the time that pop ups are open globally in Firefox.
Support is also among one of the best that I have come across recently.
Give the add-on a test run. It is all down to personal preferences but I do not think that you will be disappointed. The only problem that I found when comparing Update Scanner / Brief / SiteDelta was that Update Scanner would lock up Firefox completely when opening a link, so I would recommend disabling Update Scanner before using SiteDelta as there seem to be some incompatibility issues. This may perhaps be down to the combination of add-ons that I have and not affect you. Brief rss reader though seems to work quite happily alongside SiteDelta.

This review is for a previous version of the add-on (0.11.1).