it makes no difference if you use it or not the fact that it is currently on your pc and has a security patch out for it means you need to get the patch, having any program on your machine opens you up to security issues anytime an exploit is out for that program, especially need to get your flash updates and always get your java updates.

If secunia is telling you that these are high threat rated security updates I would get them. Many of the malware infections that people are getting these days are from these kinds of holes in programs like flash, adobe, java etc.

If you do not want IE8 you do not have to get it but you do have to get all critical updates for the version of IE that you do have on the pc.
If you do not want sp3 for example you do not have to get it but you do need to get any other security related updates for the pc.

are you using the secunia tool that you install on your pc? if you are when you get the report it will be presented in simple interface mode, at the very top right there is the word Advanced which is a clickable link if you click on that it will provide your info in a much more detailed format with clickable links to the fix for each.
Secunia Personal Software Inspector (PSI)
here on this screenshots page you can see the differences in the simple and advanced user interfaces.
Screenshots