Since the deadline for upgrade special is approaching I considering upgrading V4. I currently use a DVD authoring program which came with my DVD burner. Would having DVD4 with the upgrade to V7 make it worth the $135-150 ?
Given your circumstances, the way you describe them - I'd say you'll be happy with Vegas7+DVDA4 from V4 for the money - without a shadow of a doubt. I also was reluctant to go on the bandwagon for many of the pro features were likely to only ever be useful for a mid-morning brag. However the patches and features you'll have in Vegas7 would possibly be enough on their own, but with DVDA4 as well, - much as the offer will probably be similar for Vegas8+DVDA5 - I'd go with it especially in your position.
Now, here is the only caveat. Given you are careful with your money and have stuck with V4. Do please try out the V7+DVDA4 demo before you make your decision. At least see that it loads and allows you to drop media into Vegas7. Generally if your machine is good for V4 then it will be OK for V7 but it pays to test. There is also a test project you can download and burn for DVDA4. I'd recommend you do this to as it will set your expectations for how you create your workflow to pump out DVDRs. I personally find it of no issue whatsoever to have DVDArchitect generate files and then burn them in Nero. Some folks expect Sony MediaSoftware to keep abreast of all the commodity burners out there.
Set your own expectations and enjoy the demo phase. You still have time to evaluate the machine and your purchase. If you are undecided - it'll cost you $100 to buy later - or possibly the same if you wait another 12-18months. I'm happy - Vegas7 with the VGA preview options and good DV performance is very good. If you have any HDV ambitions during this 12 months - this is a very low entrance fee for the PC/NLE side.
"Generally if your machine is good for V4 then it will be OK for V7 but it pays to test."
Actually, V4 had much less stringent requirements than V7. For one thing, V4 didn't require Windows XP, and would work with my old Windows 98, so I used V4 for years for that reason. I upgraded to Win XP Pro early this year, so I didn't hesitate on the V7 + DVDA4 upgrade when it became available.
I can vouch for that. V7 works fine with ancient old Win2k SP4.
To qualify my emphasis, I use "good" above in rank to "OK" when judging the likelihood for Vegas4 die-hards of being totally satisfied with later version. Generally it is wise to update your PC every two to three years for NLE use. However Vegas does seem to be being optimized through the major releases. They are not just stuffing more and more in it to the point where folks are ignoring some of the refinements and questioning why there isn't more bulk. V7 suits me fine at the mid to low end of the videographer spectrum and I know it is good for more, not perfect - but good in the right hands and to a certain extent on the right system.
I don't believe in the universal editing tool anyway. Vegas provides a significant contribution to the set of tools I do use.